diff --git a/__tests__/attest.test.ts b/__tests__/attest.test.ts
deleted file mode 100644
index f6e64ff..0000000
--- a/__tests__/attest.test.ts
+++ /dev/null
@@ -1,195 +0,0 @@
-import { jest } from '@jest/globals'
-import type { Descriptor } from '@sigstore/oci'
-// Mock functions
-const mockGetOctokit = jest.fn()
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
-const mockAttest = jest.fn<() => Promise<any>>()
-const mockCreateStorageRecord = jest.fn<() => Promise<number[]>>()
-const mockGetRegistryCredentials = jest.fn()
-const mockAttachArtifactToImage = jest.fn<() => Promise<Descriptor>>()
-
-// Mock @actions/github
-jest.unstable_mockModule('@actions/github', () => ({
-  getOctokit: mockGetOctokit,
-  context: {
-    repo: { owner: 'foo', repo: 'bar' },
-    payload: { repository: { visibility: 'private' } }
-  }
-}))
-
-// Mock @actions/attest
-jest.unstable_mockModule('@actions/attest', () => ({
-  attest: mockAttest,
-  createStorageRecord: mockCreateStorageRecord
-}))
-
-// Mock @sigstore/oci
-jest.unstable_mockModule('@sigstore/oci', () => ({
-  getRegistryCredentials: mockGetRegistryCredentials,
-  attachArtifactToImage: mockAttachArtifactToImage
-}))
-
-// Dynamic imports after mocking
-const { createAttestation, repoOwnerIsOrg } = await import('../src/attest')
-
-const subjectName = 'ghcr.io/foo/bar'
-const subjectDigest =
-  'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32'
-
-const predicate = {
-  type: 'https://in-toto.io/attestation/release/v0.1',
-  params: {}
-}
-
-describe('repoOwnerIsOrg', () => {
-  beforeEach(() => {
-    jest.clearAllMocks()
-  })
-
-  it('returns true when repo owner is an organization', async () => {
-    mockGetOctokit.mockReturnValue({
-      rest: {
-        repos: {
-          get: jest
-            .fn<() => Promise<{ data: { owner: { type: string } } }>>()
-            .mockResolvedValue({
-              data: { owner: { type: 'Organization' } }
-            })
-        }
-      }
-    })
-
-    const result = await repoOwnerIsOrg('gh-token')
-    expect(result).toBe(true)
-  })
-
-  it('returns false when repo owner is a user', async () => {
-    mockGetOctokit.mockReturnValue({
-      rest: {
-        repos: {
-          // eslint-disable-next-line @typescript-eslint/no-explicit-any
-          get: jest.fn<() => Promise<any>>().mockResolvedValue({
-            data: { owner: { type: 'User' } }
-          })
-        }
-      }
-    })
-
-    const result = await repoOwnerIsOrg('gh-token')
-    expect(result).toBe(false)
-  })
-})
-
-describe('createAttestation', () => {
-  beforeEach(() => {
-    jest.clearAllMocks()
-
-    // Default mock implementations
-    mockAttest.mockResolvedValue({
-      bundle: { mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json' },
-      certificate: 'cert',
-      tlogID: 'tlog-123',
-      attestationID: 'att-123'
-    })
-
-    mockGetRegistryCredentials.mockReturnValue({
-      username: 'user',
-      password: 'pass'
-    })
-
-    mockAttachArtifactToImage.mockResolvedValue({
-      digest: 'sha256:abc123',
-      mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json',
-      size: 100
-    })
-  })
-
-  describe('when createStorageRecord is false', () => {
-    it('skips storage record creation', async () => {
-      const subjects = [
-        {
-          name: subjectName,
-          digest: { sha256: subjectDigest.replace('sha256:', '') }
-        }
-      ]
-
-      const result = await createAttestation(subjects, predicate, {
-        sigstoreInstance: 'github',
-        pushToRegistry: true,
-        createStorageRecord: false,
-        githubToken: 'gh-token'
-      })
-
-      expect(result.attestationDigest).toBe('sha256:abc123')
-      expect(mockCreateStorageRecord).not.toHaveBeenCalled()
-    })
-  })
-
-  describe('when storage records are empty', () => {
-    beforeEach(() => {
-      mockGetOctokit.mockReturnValue({
-        rest: {
-          repos: {
-            // eslint-disable-next-line @typescript-eslint/no-explicit-any
-            get: jest.fn<() => Promise<any>>().mockResolvedValue({
-              data: { owner: { type: 'Organization' } }
-            })
-          }
-        }
-      })
-      mockCreateStorageRecord.mockResolvedValue([])
-    })
-
-    it('handles empty storage records gracefully', async () => {
-      const subjects = [
-        {
-          name: subjectName,
-          digest: { sha256: subjectDigest.replace('sha256:', '') }
-        }
-      ]
-
-      const result = await createAttestation(subjects, predicate, {
-        sigstoreInstance: 'github',
-        pushToRegistry: true,
-        createStorageRecord: true,
-        githubToken: 'gh-token'
-      })
-
-      expect(result.attestationDigest).toBe('sha256:abc123')
-    })
-  })
-
-  describe('when subject has unsupported protocol', () => {
-    beforeEach(() => {
-      mockGetOctokit.mockReturnValue({
-        rest: {
-          repos: {
-            // eslint-disable-next-line @typescript-eslint/no-explicit-any
-            get: jest.fn<() => Promise<any>>().mockResolvedValue({
-              data: { owner: { type: 'Organization' } }
-            })
-          }
-        }
-      })
-      mockCreateStorageRecord.mockResolvedValue([123])
-    })
-
-    it('handles unsupported protocol gracefully', async () => {
-      const subjects = [
-        {
-          name: 'http://registry.example.com/foo/bar',
-          digest: { sha256: subjectDigest.replace('sha256:', '') }
-        }
-      ]
-
-      const result = await createAttestation(subjects, predicate, {
-        sigstoreInstance: 'github',
-        pushToRegistry: true,
-        createStorageRecord: true,
-        githubToken: 'gh-token'
-      })
-
-      expect(result.attestationDigest).toBe('sha256:abc123')
-    })
-  })
-})
diff --git a/__tests__/fixtures/mocks.ts b/__tests__/fixtures/mocks.ts
new file mode 100644
index 0000000..fc2a1db
--- /dev/null
+++ b/__tests__/fixtures/mocks.ts
@@ -0,0 +1,253 @@
+import type { Attestation, Predicate, Subject } from '@actions/attest'
+import { jest } from '@jest/globals'
+import type { RestEndpointMethodTypes } from '@octokit/plugin-rest-endpoint-methods'
+import type { Descriptor } from '@sigstore/oci'
+
+// =============================================================================
+// @actions/core mock factory
+// =============================================================================
+
+export type CoreMock = {
+  info: jest.Mock
+  warning: jest.Mock
+  debug: jest.Mock
+  startGroup: jest.Mock
+  endGroup: jest.Mock
+  setOutput: jest.Mock
+  setFailed: jest.Mock
+  summary: SummaryMock
+}
+
+export type SummaryMock = {
+  write: jest.Mock
+  addRaw: jest.Mock
+  addHeading: jest.Mock
+  addLink: jest.Mock
+  addTable: jest.Mock
+  addBreak: jest.Mock
+  addSeparator: jest.Mock
+  addQuote: jest.Mock
+  addCodeBlock: jest.Mock
+  addList: jest.Mock
+  addImage: jest.Mock
+  addDetails: jest.Mock
+  addEOL: jest.Mock
+  emptyBuffer: jest.Mock
+  stringify: jest.Mock
+  isEmptyBuffer: jest.Mock
+  clear: jest.Mock
+}
+
+export const createSummaryMock = (): SummaryMock => {
+  const mock: SummaryMock = {
+    write: jest.fn(),
+    addRaw: jest.fn(),
+    addHeading: jest.fn(),
+    addLink: jest.fn(),
+    addTable: jest.fn(),
+    addBreak: jest.fn(),
+    addSeparator: jest.fn(),
+    addQuote: jest.fn(),
+    addCodeBlock: jest.fn(),
+    addList: jest.fn(),
+    addImage: jest.fn(),
+    addDetails: jest.fn(),
+    addEOL: jest.fn(),
+    emptyBuffer: jest.fn(),
+    stringify: jest.fn().mockReturnValue(''),
+    isEmptyBuffer: jest.fn().mockReturnValue(true),
+    clear: jest.fn()
+  }
+  // Make chainable
+  for (const key of Object.keys(mock) as (keyof SummaryMock)[]) {
+    if (key !== 'stringify' && key !== 'isEmptyBuffer') {
+      mock[key].mockReturnThis()
+    }
+  }
+  return mock
+}
+
+export const createCoreMock = (): CoreMock => ({
+  info: jest.fn(),
+  warning: jest.fn(),
+  debug: jest.fn(),
+  startGroup: jest.fn(),
+  endGroup: jest.fn(),
+  setOutput: jest.fn(),
+  setFailed: jest.fn(),
+  summary: createSummaryMock()
+})
+
+// =============================================================================
+// @actions/github mock factory
+// =============================================================================
+
+export type GitHubContextMock = {
+  repo: { owner: string; repo: string }
+  payload: { repository?: { visibility: string } }
+  serverUrl: string
+}
+
+export const createGitHubContextMock = (
+  overrides: Partial<GitHubContextMock> = {}
+): GitHubContextMock => ({
+  repo: { owner: 'test-owner', repo: 'test-repo' },
+  payload: { repository: { visibility: 'public' } },
+  serverUrl: 'https://github.com',
+  ...overrides
+})
+
+export type OctokitMock = {
+  rest: {
+    repos: {
+      get: jest.Mock
+    }
+  }
+}
+
+export const createOctokitMock = (
+  ownerType: 'Organization' | 'User' = 'Organization'
+): OctokitMock => ({
+  rest: {
+    repos: {
+      get: jest
+        .fn<RestEndpointMethodTypes['repos']['get']['response']>()
+        .mockResolvedValue({
+          data: { owner: { type: ownerType } }
+        })
+    }
+  }
+})
+
+// =============================================================================
+// @actions/attest mock factory
+// =============================================================================
+
+export type AttestMock = {
+  attest: jest.Mock
+  buildSLSAProvenancePredicate: jest.Mock
+  createStorageRecord: jest.Mock
+}
+
+export const createAttestMock = (): AttestMock => ({
+  attest: jest.fn(),
+  buildSLSAProvenancePredicate: jest.fn(),
+  createStorageRecord: jest.fn()
+})
+
+export const createAttestationResult = (
+  overrides: Partial<Attestation> = {}
+): Attestation => ({
+  bundle: {
+    mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json' as const,
+    verificationMaterial: {
+      certificate: { rawBytes: '' },
+      publicKey: undefined,
+      x509CertificateChain: undefined,
+      tlogEntries: [],
+      timestampVerificationData: undefined
+    },
+    dsseEnvelope: {
+      payload: '',
+      payloadType: '',
+      signatures: []
+    },
+    messageSignature: undefined
+  },
+  certificate: '-----BEGIN CERTIFICATE-----\ntest\n-----END CERTIFICATE-----',
+  tlogID: 'tlog-123',
+  attestationID: 'att-123',
+  ...overrides
+})
+
+// =============================================================================
+// @sigstore/oci mock factory
+// =============================================================================
+
+export type OciMock = {
+  getRegistryCredentials: jest.Mock
+  attachArtifactToImage: jest.Mock
+}
+
+export const createOciMock = (): OciMock => ({
+  getRegistryCredentials: jest.fn().mockReturnValue({
+    username: 'test-user',
+    password: 'test-pass'
+  }),
+  attachArtifactToImage: jest
+    .fn<() => Promise<Descriptor>>()
+    .mockResolvedValue({
+      digest: 'sha256:abc123def456',
+      mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json',
+      size: 1234
+    })
+})
+
+// =============================================================================
+// Common test data
+// =============================================================================
+
+export const TEST_SUBJECT: Subject = {
+  name: 'test-artifact',
+  digest: {
+    sha256: '7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32'
+  }
+}
+
+export const TEST_SUBJECT_WITH_REGISTRY: Subject = {
+  name: 'ghcr.io/test-owner/test-repo',
+  digest: {
+    sha256: '7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32'
+  }
+}
+
+export const TEST_PREDICATE: Predicate = {
+  type: 'https://example.com/predicate/v1',
+  params: { foo: 'bar' }
+}
+
+export const TEST_PROVENANCE_PREDICATE: Predicate = {
+  type: 'https://slsa.dev/provenance/v1',
+  params: {
+    buildDefinition: {
+      buildType: 'https://actions.github.io/buildtypes/workflow/v1'
+    },
+    runDetails: {
+      builder: { id: 'https://github.com/actions/runner' }
+    }
+  }
+}
+
+// =============================================================================
+// Environment helpers
+// =============================================================================
+
+export const setupTestEnvironment = (
+  env: Record<string, string> = {}
+): (() => void) => {
+  const originalEnv = { ...process.env }
+
+  process.env = {
+    ...process.env,
+    ACTIONS_ID_TOKEN_REQUEST_URL: 'https://token.url',
+    ACTIONS_ID_TOKEN_REQUEST_TOKEN: 'test-token',
+    RUNNER_TEMP: '/tmp',
+    ...env
+  }
+
+  return () => {
+    process.env = originalEnv
+  }
+}
+
+// =============================================================================
+// OIDC token helpers
+// =============================================================================
+
+export const createOidcToken = (subject = 'test@example.com'): string => {
+  const payload = {
+    sub: subject,
+    iss: 'https://token.actions.githubusercontent.com'
+  }
+  return `.${Buffer.from(JSON.stringify(payload)).toString('base64')}.`
+}
diff --git a/__tests__/fixtures/samples/cyclonedx-sbom.json b/__tests__/fixtures/samples/cyclonedx-sbom.json
new file mode 100644
index 0000000..bd1d83d
--- /dev/null
+++ b/__tests__/fixtures/samples/cyclonedx-sbom.json
@@ -0,0 +1,13 @@
+{
+  "bomFormat": "CycloneDX",
+  "specVersion": "1.4",
+  "serialNumber": "urn:uuid:12345678-1234-1234-1234-123456789012",
+  "version": 1,
+  "components": [
+    {
+      "type": "library",
+      "name": "test-component",
+      "version": "1.0.0"
+    }
+  ]
+}
diff --git a/__tests__/fixtures/samples/predicate.json b/__tests__/fixtures/samples/predicate.json
new file mode 100644
index 0000000..6d837d4
--- /dev/null
+++ b/__tests__/fixtures/samples/predicate.json
@@ -0,0 +1,9 @@
+{
+  "buildType": "https://example.com/build/v1",
+  "builder": {
+    "id": "https://github.com/actions/runner"
+  },
+  "metadata": {
+    "buildStartedOn": "2024-01-01T00:00:00Z"
+  }
+}
diff --git a/__tests__/fixtures/samples/spdx-sbom.json b/__tests__/fixtures/samples/spdx-sbom.json
new file mode 100644
index 0000000..7ed4131
--- /dev/null
+++ b/__tests__/fixtures/samples/spdx-sbom.json
@@ -0,0 +1,15 @@
+{
+  "spdxVersion": "SPDX-2.3",
+  "SPDXID": "SPDXRef-DOCUMENT",
+  "name": "test-package",
+  "dataLicense": "CC0-1.0",
+  "documentNamespace": "https://example.com/test-package",
+  "packages": [
+    {
+      "SPDXID": "SPDXRef-Package",
+      "name": "test-package",
+      "versionInfo": "1.0.0",
+      "downloadLocation": "https://example.com/test-package-1.0.0.tar.gz"
+    }
+  ]
+}
diff --git a/__tests__/index.test.ts b/__tests__/index.test.ts
index 90c8107..8038e57 100644
--- a/__tests__/index.test.ts
+++ b/__tests__/index.test.ts
@@ -1,6 +1,3 @@
-/**
- * Unit tests for the action's entrypoint, src/index.ts
- */
 import { jest } from '@jest/globals'
 
 // Mock functions
@@ -22,14 +19,53 @@ jest.unstable_mockModule('../src/main', () => ({
 describe('index', () => {
   beforeEach(() => {
     jest.clearAllMocks()
-    mockGetBooleanInput.mockReturnValue(false)
     mockGetInput.mockReturnValue('')
+    mockGetBooleanInput.mockReturnValue(false)
   })
 
-  it('calls run when imported', async () => {
-    // Dynamic import after mocking
+  it('should call run with inputs from core.getInput', async () => {
+    mockGetInput.mockImplementation((name: string) => {
+      const inputs: Record<string, string> = {
+        'subject-path': '/path/to/subject',
+        'subject-name': 'my-artifact',
+        'subject-digest': '',
+        'subject-checksums': '',
+        'predicate-type': 'https://example.com/predicate',
+        predicate: '{}',
+        'predicate-path': '',
+        'sbom-path': '',
+        'github-token': 'test-token'
+      }
+      return inputs[name] || ''
+    })
+
+    mockGetBooleanInput.mockImplementation((name: string) => {
+      const inputs: Record<string, boolean> = {
+        'push-to-registry': false,
+        'create-storage-record': true,
+        'show-summary': true,
+        'private-signing': false
+      }
+      return inputs[name] || false
+    })
+
+    // Dynamic import triggers the module
     await import('../src/index')
 
-    expect(mockRun).toHaveBeenCalled()
+    expect(mockRun).toHaveBeenCalledWith({
+      subjectPath: '/path/to/subject',
+      subjectName: 'my-artifact',
+      subjectDigest: '',
+      subjectChecksums: '',
+      predicateType: 'https://example.com/predicate',
+      predicate: '{}',
+      predicatePath: '',
+      sbomPath: '',
+      githubToken: 'test-token',
+      pushToRegistry: false,
+      createStorageRecord: true,
+      showSummary: true,
+      privateSigning: false
+    })
   })
 })
diff --git a/__tests__/integration/attest.test.ts b/__tests__/integration/attest.test.ts
new file mode 100644
index 0000000..438c667
--- /dev/null
+++ b/__tests__/integration/attest.test.ts
@@ -0,0 +1,228 @@
+import { jest } from '@jest/globals'
+import {
+  createAttestationResult,
+  createGitHubContextMock,
+  createOctokitMock,
+  TEST_PREDICATE,
+  TEST_SUBJECT_WITH_REGISTRY
+} from '../fixtures/mocks'
+
+import type { Attestation } from '@actions/attest'
+import type { Descriptor } from '@sigstore/oci'
+
+// Mock functions
+const mockGetOctokit = jest.fn()
+const mockAttest = jest.fn<() => Promise<Attestation>>()
+const mockCreateStorageRecord = jest.fn<() => Promise<number[]>>()
+const mockGetRegistryCredentials = jest.fn()
+const mockAttachArtifactToImage = jest.fn<() => Promise<Descriptor>>()
+
+// Mutable context for tests
+const mockContext = createGitHubContextMock()
+
+// Mock @actions/github
+jest.unstable_mockModule('@actions/github', () => ({
+  getOctokit: mockGetOctokit,
+  context: mockContext
+}))
+
+// Mock @actions/attest
+jest.unstable_mockModule('@actions/attest', () => ({
+  attest: mockAttest,
+  createStorageRecord: mockCreateStorageRecord
+}))
+
+// Mock @sigstore/oci
+jest.unstable_mockModule('@sigstore/oci', () => ({
+  getRegistryCredentials: mockGetRegistryCredentials,
+  attachArtifactToImage: mockAttachArtifactToImage
+}))
+
+// Dynamic imports after mocking
+const { createAttestation, repoOwnerIsOrg } = await import('../../src/attest')
+
+describe('repoOwnerIsOrg', () => {
+  beforeEach(() => {
+    jest.clearAllMocks()
+  })
+
+  it('should return true when repo owner is an Organization', async () => {
+    mockGetOctokit.mockReturnValue(createOctokitMock('Organization'))
+
+    const result = await repoOwnerIsOrg('test-token')
+
+    expect(result).toBe(true)
+    expect(mockGetOctokit).toHaveBeenCalledWith('test-token')
+  })
+
+  it('should return false when repo owner is a User', async () => {
+    mockGetOctokit.mockReturnValue(createOctokitMock('User'))
+
+    const result = await repoOwnerIsOrg('test-token')
+
+    expect(result).toBe(false)
+  })
+})
+
+describe('createAttestation', () => {
+  const defaultOpts = {
+    sigstoreInstance: 'github' as const,
+    pushToRegistry: false,
+    createStorageRecord: false,
+    githubToken: 'test-token'
+  }
+
+  beforeEach(() => {
+    jest.clearAllMocks()
+
+    mockAttest.mockResolvedValue(createAttestationResult())
+    mockGetRegistryCredentials.mockReturnValue({
+      username: 'test-user',
+      password: 'test-pass'
+    })
+    mockAttachArtifactToImage.mockResolvedValue({
+      digest: 'sha256:attestation-digest',
+      mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json',
+      size: 1234
+    })
+    mockCreateStorageRecord.mockResolvedValue([12345])
+    mockGetOctokit.mockReturnValue(createOctokitMock('Organization'))
+  })
+
+  describe('basic attestation', () => {
+    it('should call attest with correct parameters', async () => {
+      const subjects = [TEST_SUBJECT_WITH_REGISTRY]
+
+      await createAttestation(subjects, TEST_PREDICATE, defaultOpts)
+
+      expect(mockAttest).toHaveBeenCalledWith({
+        subjects,
+        predicateType: TEST_PREDICATE.type,
+        predicate: TEST_PREDICATE.params,
+        sigstore: 'github',
+        token: 'test-token'
+      })
+    })
+
+    it('should return attestation result', async () => {
+      const subjects = [TEST_SUBJECT_WITH_REGISTRY]
+
+      const result = await createAttestation(
+        subjects,
+        TEST_PREDICATE,
+        defaultOpts
+      )
+
+      expect(result.attestationID).toBe('att-123')
+      expect(result.certificate).toContain('BEGIN CERTIFICATE')
+      expect(result.tlogID).toBe('tlog-123')
+    })
+  })
+
+  describe('registry push', () => {
+    const pushOpts = { ...defaultOpts, pushToRegistry: true }
+
+    it('should push attestation to registry when enabled', async () => {
+      const subjects = [TEST_SUBJECT_WITH_REGISTRY]
+
+      const result = await createAttestation(subjects, TEST_PREDICATE, pushOpts)
+
+      expect(mockGetRegistryCredentials).toHaveBeenCalledWith(subjects[0].name)
+      expect(mockAttachArtifactToImage).toHaveBeenCalled()
+      expect(result.attestationDigest).toBe('sha256:attestation-digest')
+    })
+
+    it('should skip registry push for multiple subjects', async () => {
+      const subjects = [TEST_SUBJECT_WITH_REGISTRY, TEST_SUBJECT_WITH_REGISTRY]
+
+      await createAttestation(subjects, TEST_PREDICATE, pushOpts)
+
+      expect(mockAttachArtifactToImage).not.toHaveBeenCalled()
+    })
+  })
+
+  describe('storage record creation', () => {
+    const storageOpts = {
+      ...defaultOpts,
+      pushToRegistry: true,
+      createStorageRecord: true
+    }
+
+    it('should create storage record when enabled and owner is org', async () => {
+      const subjects = [TEST_SUBJECT_WITH_REGISTRY]
+
+      const result = await createAttestation(
+        subjects,
+        TEST_PREDICATE,
+        storageOpts
+      )
+
+      expect(mockCreateStorageRecord).toHaveBeenCalled()
+      expect(result.storageRecordIds).toEqual([12345])
+    })
+
+    it('should skip storage record when owner is User', async () => {
+      mockGetOctokit.mockReturnValue(createOctokitMock('User'))
+      const subjects = [TEST_SUBJECT_WITH_REGISTRY]
+
+      const result = await createAttestation(
+        subjects,
+        TEST_PREDICATE,
+        storageOpts
+      )
+
+      expect(mockCreateStorageRecord).not.toHaveBeenCalled()
+      expect(result.storageRecordIds).toBeUndefined()
+    })
+
+    it('should skip storage record when createStorageRecord is false', async () => {
+      const subjects = [TEST_SUBJECT_WITH_REGISTRY]
+      const opts = { ...storageOpts, createStorageRecord: false }
+
+      await createAttestation(subjects, TEST_PREDICATE, opts)
+
+      expect(mockCreateStorageRecord).not.toHaveBeenCalled()
+    })
+
+    it('should handle empty storage records gracefully', async () => {
+      mockCreateStorageRecord.mockResolvedValue([])
+      const subjects = [TEST_SUBJECT_WITH_REGISTRY]
+
+      const result = await createAttestation(
+        subjects,
+        TEST_PREDICATE,
+        storageOpts
+      )
+
+      expect(result.storageRecordIds).toEqual([])
+    })
+
+    it('should continue when storage record creation fails', async () => {
+      mockCreateStorageRecord.mockRejectedValue(new Error('Permission denied'))
+      const subjects = [TEST_SUBJECT_WITH_REGISTRY]
+
+      // Should not throw
+      const result = await createAttestation(
+        subjects,
+        TEST_PREDICATE,
+        storageOpts
+      )
+
+      expect(result.attestationID).toBe('att-123')
+      expect(result.storageRecordIds).toBeUndefined()
+    })
+  })
+
+  describe('sigstore instance selection', () => {
+    it('should use public-good sigstore instance when specified', async () => {
+      const subjects = [TEST_SUBJECT_WITH_REGISTRY]
+      const opts = { ...defaultOpts, sigstoreInstance: 'public-good' as const }
+
+      await createAttestation(subjects, TEST_PREDICATE, opts)
+
+      expect(mockAttest).toHaveBeenCalledWith(
+        expect.objectContaining({ sigstore: 'public-good' })
+      )
+    })
+  })
+})
diff --git a/__tests__/integration/main.test.ts b/__tests__/integration/main.test.ts
new file mode 100644
index 0000000..61d7e33
--- /dev/null
+++ b/__tests__/integration/main.test.ts
@@ -0,0 +1,454 @@
+import { jest } from '@jest/globals'
+import fs from 'fs/promises'
+import os from 'os'
+import path from 'path'
+import {
+  createAttestationResult,
+  createOctokitMock,
+  TEST_PROVENANCE_PREDICATE
+} from '../fixtures/mocks'
+
+import type { Attestation, Predicate } from '@actions/attest'
+import type { Descriptor } from '@sigstore/oci'
+import type { RunInputs } from '../../src/main'
+
+// Create persistent mock functions
+const infoMock = jest.fn()
+const warningMock = jest.fn()
+const debugMock = jest.fn()
+const startGroupMock = jest.fn()
+const endGroupMock = jest.fn()
+const setOutputMock = jest.fn()
+const setFailedMock = jest.fn()
+
+// Create chainable summary mock
+const summaryMock = {
+  write: jest.fn().mockReturnThis(),
+  addRaw: jest.fn().mockReturnThis(),
+  addHeading: jest.fn().mockReturnThis(),
+  addLink: jest.fn().mockReturnThis(),
+  addTable: jest.fn().mockReturnThis(),
+  addBreak: jest.fn().mockReturnThis(),
+  addSeparator: jest.fn().mockReturnThis(),
+  addQuote: jest.fn().mockReturnThis(),
+  addCodeBlock: jest.fn().mockReturnThis(),
+  addList: jest.fn().mockReturnThis(),
+  addImage: jest.fn().mockReturnThis(),
+  addDetails: jest.fn().mockReturnThis(),
+  addEOL: jest.fn().mockReturnThis(),
+  emptyBuffer: jest.fn().mockReturnThis(),
+  stringify: jest.fn().mockReturnValue(''),
+  isEmptyBuffer: jest.fn().mockReturnValue(true),
+  clear: jest.fn().mockReturnThis()
+}
+
+const mockGetOctokit = jest.fn()
+const mockAttest = jest.fn<() => Promise<Attestation>>()
+const mockBuildSLSAProvenancePredicate = jest.fn<() => Promise<Predicate>>()
+const mockCreateStorageRecord = jest.fn<() => Promise<number[]>>()
+const mockGetRegistryCredentials = jest.fn()
+const mockAttachArtifactToImage = jest.fn<() => Promise<Descriptor>>()
+
+// Mutable context for tests
+const mockContext = {
+  repo: { owner: 'test-owner', repo: 'test-repo' },
+  payload: { repository: { visibility: 'private' } },
+  serverUrl: 'https://github.com'
+}
+
+// Mock @actions/core
+jest.unstable_mockModule('@actions/core', () => ({
+  info: infoMock,
+  warning: warningMock,
+  debug: debugMock,
+  startGroup: startGroupMock,
+  endGroup: endGroupMock,
+  setOutput: setOutputMock,
+  setFailed: setFailedMock,
+  summary: summaryMock
+}))
+
+// Mock @actions/github
+jest.unstable_mockModule('@actions/github', () => ({
+  getOctokit: mockGetOctokit,
+  context: mockContext
+}))
+
+// Mock @actions/attest
+jest.unstable_mockModule('@actions/attest', () => ({
+  attest: mockAttest,
+  buildSLSAProvenancePredicate: mockBuildSLSAProvenancePredicate,
+  createStorageRecord: mockCreateStorageRecord
+}))
+
+// Mock @sigstore/oci
+jest.unstable_mockModule('@sigstore/oci', () => ({
+  getRegistryCredentials: mockGetRegistryCredentials,
+  attachArtifactToImage: mockAttachArtifactToImage
+}))
+
+// Dynamic import after mocking
+const { run } = await import('../../src/main')
+
+const defaultInputs: RunInputs = {
+  predicate: '',
+  predicateType: '',
+  predicatePath: '',
+  sbomPath: '',
+  subjectName: '',
+  subjectDigest: '',
+  subjectPath: '',
+  subjectChecksums: '',
+  pushToRegistry: false,
+  createStorageRecord: false,
+  showSummary: false,
+  githubToken: 'test-token',
+  privateSigning: false
+}
+
+describe('run', () => {
+  let tempDir: string
+  const originalEnv = { ...process.env }
+
+  beforeEach(async () => {
+    jest.clearAllMocks()
+
+    // Reset chainable summary mocks
+    for (const key of Object.keys(summaryMock)) {
+      if (key !== 'stringify' && key !== 'isEmptyBuffer') {
+        ;(
+          summaryMock[key as keyof typeof summaryMock] as jest.Mock
+        ).mockReturnThis()
+      }
+    }
+
+    mockAttest.mockResolvedValue(createAttestationResult())
+    mockBuildSLSAProvenancePredicate.mockResolvedValue(
+      TEST_PROVENANCE_PREDICATE
+    )
+    mockCreateStorageRecord.mockResolvedValue([12345])
+    mockGetOctokit.mockReturnValue(createOctokitMock('Organization'))
+    mockGetRegistryCredentials.mockReturnValue({ username: 'u', password: 'p' })
+    mockAttachArtifactToImage.mockResolvedValue({
+      digest: 'sha256:abc',
+      mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json',
+      size: 100
+    })
+
+    // Reset context
+    mockContext.repo = { owner: 'test-owner', repo: 'test-repo' }
+    mockContext.payload = { repository: { visibility: 'private' } }
+
+    // Create temp directory
+    tempDir = await fs.mkdtemp(path.join(os.tmpdir(), 'main-test-'))
+
+    // Set required environment
+    process.env.ACTIONS_ID_TOKEN_REQUEST_URL = 'https://token.url'
+    process.env.ACTIONS_ID_TOKEN_REQUEST_TOKEN = 'test-token'
+    process.env.RUNNER_TEMP = tempDir
+  })
+
+  afterEach(async () => {
+    process.env = { ...originalEnv }
+    await fs.rm(tempDir, { recursive: true, force: true })
+  })
+
+  describe('environment validation', () => {
+    it('should fail when ACTIONS_ID_TOKEN_REQUEST_URL is not set', async () => {
+      delete process.env.ACTIONS_ID_TOKEN_REQUEST_URL
+
+      await run({
+        ...defaultInputs,
+        subjectName: 'artifact',
+        subjectDigest:
+          'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32',
+        predicateType: 'https://example.com/predicate',
+        predicate: '{}'
+      })
+
+      expect(setFailedMock).toHaveBeenCalledWith(
+        expect.objectContaining({
+          message: expect.stringContaining('id-token')
+        })
+      )
+    })
+  })
+
+  describe('subject validation', () => {
+    it('should fail when no subject inputs are provided', async () => {
+      await run(defaultInputs)
+
+      expect(setFailedMock).toHaveBeenCalledWith(
+        expect.objectContaining({
+          message: expect.stringContaining('subject-path')
+        })
+      )
+    })
+  })
+
+  describe('attestation type detection', () => {
+    it('should detect provenance attestation when no predicate inputs provided', async () => {
+      await run({
+        ...defaultInputs,
+        subjectName: 'artifact',
+        subjectDigest:
+          'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32'
+      })
+
+      expect(infoMock).toHaveBeenCalledWith(
+        'Attestation type: Build Provenance'
+      )
+      expect(mockBuildSLSAProvenancePredicate).toHaveBeenCalled()
+    })
+
+    it('should detect custom attestation when predicate inputs provided', async () => {
+      await run({
+        ...defaultInputs,
+        subjectName: 'artifact',
+        subjectDigest:
+          'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32',
+        predicateType: 'https://example.com/predicate',
+        predicate: '{}'
+      })
+
+      expect(infoMock).toHaveBeenCalledWith('Attestation type: Custom')
+      expect(mockBuildSLSAProvenancePredicate).not.toHaveBeenCalled()
+    })
+
+    it('should detect SBOM attestation when sbom-path provided', async () => {
+      const sbomPath = path.join(tempDir, 'sbom.json')
+      await fs.writeFile(
+        sbomPath,
+        JSON.stringify({
+          spdxVersion: 'SPDX-2.3',
+          SPDXID: 'SPDXRef-DOCUMENT',
+          name: 'test'
+        })
+      )
+
+      await run({
+        ...defaultInputs,
+        subjectName: 'artifact',
+        subjectDigest:
+          'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32',
+        sbomPath
+      })
+
+      expect(infoMock).toHaveBeenCalledWith('Attestation type: SBOM')
+    })
+
+    it('should fail when sbom-path is combined with predicate inputs', async () => {
+      await run({
+        ...defaultInputs,
+        subjectName: 'artifact',
+        subjectDigest:
+          'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32',
+        sbomPath: '/path/to/sbom.json',
+        predicateType: 'https://example.com/predicate'
+      })
+
+      expect(setFailedMock).toHaveBeenCalledWith(
+        expect.objectContaining({
+          message: expect.stringContaining(
+            'Cannot specify sbom-path together with'
+          )
+        })
+      )
+    })
+  })
+
+  describe('successful attestation', () => {
+    const validInputs: RunInputs = {
+      ...defaultInputs,
+      subjectName: 'artifact',
+      subjectDigest:
+        'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32',
+      predicateType: 'https://example.com/predicate',
+      predicate: '{}'
+    }
+
+    it('should create attestation successfully', async () => {
+      await run(validInputs)
+
+      expect(setFailedMock).not.toHaveBeenCalled()
+      expect(mockAttest).toHaveBeenCalled()
+    })
+
+    it('should set output for attestation-id', async () => {
+      await run(validInputs)
+
+      expect(setOutputMock).toHaveBeenCalledWith('attestation-id', 'att-123')
+    })
+
+    it('should set output for attestation-url', async () => {
+      await run(validInputs)
+
+      expect(setOutputMock).toHaveBeenCalledWith(
+        'attestation-url',
+        'https://github.com/test-owner/test-repo/attestations/att-123'
+      )
+    })
+
+    it('should set output for bundle-path', async () => {
+      await run(validInputs)
+
+      expect(setOutputMock).toHaveBeenCalledWith(
+        'bundle-path',
+        expect.stringContaining('attestation.json')
+      )
+    })
+
+    it('should write attestation bundle to file', async () => {
+      await run(validInputs)
+
+      const bundlePath = setOutputMock.mock.calls.find(
+        (call: unknown[]) => call[0] === 'bundle-path'
+      )?.[1] as string
+
+      const content = await fs.readFile(bundlePath, 'utf-8')
+      expect(content).toContain('mediaType')
+    })
+  })
+
+  describe('sigstore instance selection', () => {
+    const validInputs: RunInputs = {
+      ...defaultInputs,
+      subjectName: 'artifact',
+      subjectDigest:
+        'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32',
+      predicateType: 'https://example.com/predicate',
+      predicate: '{}'
+    }
+
+    it('should use github sigstore for private repos', async () => {
+      mockContext.payload = { repository: { visibility: 'private' } }
+
+      await run(validInputs)
+
+      expect(mockAttest).toHaveBeenCalledWith(
+        expect.objectContaining({ sigstore: 'github' })
+      )
+    })
+
+    it('should use public-good sigstore for public repos', async () => {
+      mockContext.payload = { repository: { visibility: 'public' } }
+
+      await run(validInputs)
+
+      expect(mockAttest).toHaveBeenCalledWith(
+        expect.objectContaining({ sigstore: 'public-good' })
+      )
+    })
+
+    it('should use github sigstore when privateSigning is true', async () => {
+      mockContext.payload = { repository: { visibility: 'public' } }
+
+      await run({ ...validInputs, privateSigning: true })
+
+      expect(mockAttest).toHaveBeenCalledWith(
+        expect.objectContaining({ sigstore: 'github' })
+      )
+    })
+  })
+
+  describe('multiple subjects', () => {
+    it('should handle multiple subjects from glob pattern', async () => {
+      // Create test files
+      for (let i = 0; i < 3; i++) {
+        await fs.writeFile(path.join(tempDir, `file-${i}.txt`), `content-${i}`)
+      }
+
+      await run({
+        ...defaultInputs,
+        subjectPath: path.join(tempDir, 'file-*.txt'),
+        predicateType: 'https://example.com/predicate',
+        predicate: '{}'
+      })
+
+      expect(setFailedMock).not.toHaveBeenCalled()
+      expect(infoMock).toHaveBeenCalledWith(
+        expect.stringContaining('3 subjects')
+      )
+    })
+
+    it('should fail when subject count exceeds maximum', async () => {
+      // Create too many files
+      for (let i = 0; i < 1025; i++) {
+        await fs.writeFile(path.join(tempDir, `file-${i}.txt`), `content-${i}`)
+      }
+
+      await run({
+        ...defaultInputs,
+        subjectPath: path.join(tempDir, 'file-*.txt'),
+        predicateType: 'https://example.com/predicate',
+        predicate: '{}'
+      })
+
+      expect(setFailedMock).toHaveBeenCalledWith(
+        expect.objectContaining({
+          message: expect.stringContaining('Too many subjects')
+        })
+      )
+    })
+  })
+
+  describe('summary output', () => {
+    const validInputs: RunInputs = {
+      ...defaultInputs,
+      subjectName: 'artifact',
+      subjectDigest:
+        'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32',
+      predicateType: 'https://example.com/predicate',
+      predicate: '{}',
+      showSummary: true
+    }
+
+    it('should write summary when showSummary is true', async () => {
+      await run(validInputs)
+
+      expect(summaryMock.addHeading).toHaveBeenCalled()
+      expect(summaryMock.write).toHaveBeenCalled()
+    })
+
+    it('should not write summary when showSummary is false', async () => {
+      await run({ ...validInputs, showSummary: false })
+
+      expect(summaryMock.write).not.toHaveBeenCalled()
+    })
+  })
+
+  describe('registry push', () => {
+    const registryInputs: RunInputs = {
+      ...defaultInputs,
+      subjectName: 'ghcr.io/test-owner/test-repo',
+      subjectDigest:
+        'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32',
+      predicateType: 'https://example.com/predicate',
+      predicate: '{}',
+      pushToRegistry: true
+    }
+
+    it('should push attestation to registry when enabled', async () => {
+      await run(registryInputs)
+
+      expect(mockAttachArtifactToImage).toHaveBeenCalled()
+    })
+
+    it('should lowercase subject name for registry push', async () => {
+      await run({
+        ...registryInputs,
+        subjectName: 'ghcr.io/TEST-OWNER/Test-Repo'
+      })
+
+      expect(mockAttest).toHaveBeenCalledWith(
+        expect.objectContaining({
+          subjects: [
+            expect.objectContaining({
+              name: 'ghcr.io/test-owner/test-repo'
+            })
+          ]
+        })
+      )
+    })
+  })
+})
diff --git a/__tests__/provenance.test.ts b/__tests__/integration/provenance.test.ts
similarity index 51%
rename from __tests__/provenance.test.ts
rename to __tests__/integration/provenance.test.ts
index 7bbe489..f81a9a2 100644
--- a/__tests__/provenance.test.ts
+++ b/__tests__/integration/provenance.test.ts
@@ -1,5 +1,6 @@
 import type { Predicate } from '@actions/attest'
 import { jest } from '@jest/globals'
+import { TEST_PROVENANCE_PREDICATE } from '../fixtures/mocks'
 
 // Mock function
 const mockBuildSLSAProvenancePredicate = jest.fn<() => Promise<Predicate>>()
@@ -10,39 +11,27 @@ jest.unstable_mockModule('@actions/attest', () => ({
 }))
 
 // Dynamic import after mocking
-const { generateProvenancePredicate } = await import('../src/provenance')
+const { generateProvenancePredicate } = await import('../../src/provenance')
 
 describe('generateProvenancePredicate', () => {
-  const mockPredicate = {
-    type: 'https://slsa.dev/provenance/v1',
-    params: {
-      buildDefinition: {
-        buildType: 'https://actions.github.io/buildtypes/workflow/v1'
-      },
-      runDetails: {
-        builder: { id: 'https://github.com/actions/runner' }
-      }
-    }
-  }
-
   beforeEach(() => {
     jest.clearAllMocks()
-    mockBuildSLSAProvenancePredicate.mockResolvedValue(mockPredicate)
+    mockBuildSLSAProvenancePredicate.mockResolvedValue(TEST_PROVENANCE_PREDICATE)
   })
 
-  it('returns the SLSA provenance predicate', async () => {
+  it('should delegate to buildSLSAProvenancePredicate', async () => {
     const result = await generateProvenancePredicate()
 
     expect(mockBuildSLSAProvenancePredicate).toHaveBeenCalledTimes(1)
-    expect(result).toEqual(mockPredicate)
+    expect(result).toEqual(TEST_PROVENANCE_PREDICATE)
   })
 
-  it('propagates errors from buildSLSAProvenancePredicate', async () => {
-    const error = new Error('Failed to build provenance')
+  it('should propagate errors from the underlying function', async () => {
+    const error = new Error('Failed to build provenance predicate')
     mockBuildSLSAProvenancePredicate.mockRejectedValue(error)
 
     await expect(generateProvenancePredicate()).rejects.toThrow(
-      'Failed to build provenance'
+      'Failed to build provenance predicate'
     )
   })
 })
diff --git a/__tests__/main.test.ts b/__tests__/main.test.ts
deleted file mode 100644
index 600b55d..0000000
--- a/__tests__/main.test.ts
+++ /dev/null
@@ -1,676 +0,0 @@
-/**
- * Unit tests for the action's main functionality, src/main.ts
- *
- * These should be run as if the action was called from a workflow.
- * Specifically, the inputs listed in `action.yml` should be set as environment
- * variables following the pattern `INPUT_<INPUT_NAME>`.
- */
-import type { Predicate } from '@actions/attest'
-import { jest } from '@jest/globals'
-import type { RunInputs } from '../src/main'
-
-// Create mock functions before mocking modules
-const infoMock = jest.fn()
-const warningMock = jest.fn()
-const startGroupMock = jest.fn()
-const endGroupMock = jest.fn()
-const setOutputMock = jest.fn()
-const setFailedMock = jest.fn()
-const debugMock = jest.fn()
-
-// OCI mocks
-const getRegCredsMock = jest.fn()
-const attachArtifactMock = jest.fn()
-
-// Attest mocks
-const attestMock = jest.fn()
-const createStorageRecordMock = jest.fn()
-
-// Local attest mocks
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
-const createAttestationMock = jest.fn<() => Promise<any>>()
-const repoOwnerIsOrgMock = jest.fn()
-
-// Provenance mock
-const generateProvenancePredicateMock = jest.fn<() => Promise<Predicate>>()
-
-// GitHub context mock
-const mockContext = {
-  repo: { owner: 'foo', repo: 'bar' },
-  payload: { repository: { visibility: 'private' } }
-}
-const mockGetOctokit = jest.fn()
-
-// Summary mock with chainable methods
-const summaryMock = {
-  write: jest.fn().mockReturnThis(),
-  addRaw: jest.fn().mockReturnThis(),
-  addHeading: jest.fn().mockReturnThis(),
-  addLink: jest.fn().mockReturnThis(),
-  addTable: jest.fn().mockReturnThis(),
-  addBreak: jest.fn().mockReturnThis(),
-  addSeparator: jest.fn().mockReturnThis(),
-  addQuote: jest.fn().mockReturnThis(),
-  addCodeBlock: jest.fn().mockReturnThis(),
-  addList: jest.fn().mockReturnThis(),
-  addImage: jest.fn().mockReturnThis(),
-  addDetails: jest.fn().mockReturnThis(),
-  addEOL: jest.fn().mockReturnThis(),
-  emptyBuffer: jest.fn().mockReturnThis(),
-  stringify: jest.fn().mockReturnValue(''),
-  isEmptyBuffer: jest.fn().mockReturnValue(true),
-  clear: jest.fn().mockReturnThis()
-}
-
-// Mock @actions/core
-jest.unstable_mockModule('@actions/core', () => ({
-  info: infoMock,
-  warning: warningMock,
-  startGroup: startGroupMock,
-  endGroup: endGroupMock,
-  setOutput: setOutputMock,
-  setFailed: setFailedMock,
-  debug: debugMock,
-  summary: summaryMock
-}))
-
-// Mock @actions/github
-jest.unstable_mockModule('@actions/github', () => ({
-  context: mockContext,
-  getOctokit: mockGetOctokit
-}))
-
-// Mock @sigstore/oci
-jest.unstable_mockModule('@sigstore/oci', () => ({
-  getRegistryCredentials: getRegCredsMock,
-  attachArtifactToImage: attachArtifactMock
-}))
-
-// Mock @actions/attest
-jest.unstable_mockModule('@actions/attest', () => ({
-  attest: attestMock,
-  createStorageRecord: createStorageRecordMock
-}))
-
-// Mock ../src/attest
-jest.unstable_mockModule('../src/attest', () => ({
-  createAttestation: createAttestationMock,
-  repoOwnerIsOrg: repoOwnerIsOrgMock
-}))
-
-// Mock ../src/provenance
-jest.unstable_mockModule('../src/provenance', () => ({
-  generateProvenancePredicate: generateProvenancePredicateMock
-}))
-
-// Dynamic imports after mocking
-const { mockFulcio, mockRekor, mockTSA } = await import('@sigstore/mock')
-const fs = (await import('fs/promises')).default
-const nock = (await import('nock')).default
-const os = (await import('os')).default
-const path = (await import('path')).default
-const { MockAgent, setGlobalDispatcher } = await import('undici')
-const { run } = await import('../src/main')
-
-// MockAgent for mocking @actions/github
-const mockAgent = new MockAgent()
-setGlobalDispatcher(mockAgent)
-
-const defaultInputs: RunInputs = {
-  predicate: '',
-  predicateType: '',
-  predicatePath: '',
-  sbomPath: '',
-  subjectName: '',
-  subjectDigest: '',
-  subjectPath: '',
-  subjectChecksums: '',
-  pushToRegistry: false,
-  createStorageRecord: true,
-  showSummary: true,
-  githubToken: '',
-  privateSigning: false
-}
-
-describe('action', () => {
-  // Capture original environment variables so we can restore after each test
-  const originalEnv = process.env
-  const originalContext = {
-    repo: { owner: 'foo', repo: 'bar' },
-    payload: { repository: { visibility: 'private' } }
-  }
-
-  // Mock OIDC token endpoint
-  const tokenURL = 'https://token.url'
-
-  // Fake an OIDC token
-  const oidcSubject = 'foo@bar.com'
-  const oidcPayload = { sub: oidcSubject, iss: '' }
-  const oidcToken = `.${Buffer.from(JSON.stringify(oidcPayload)).toString(
-    'base64'
-  )}.}`
-
-  const subjectName = 'ghcr.io/registry/foo/bar'
-  const subjectDigest =
-    'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32'
-  const predicate = '{}'
-  const predicateType = 'https://in-toto.io/attestation/release/v0.1'
-
-  const attestationID = '1234567890'
-  const storageRecordID = 987654321
-
-  beforeEach(() => {
-    jest.clearAllMocks()
-
-    nock(tokenURL)
-      .get('/')
-      .query({ audience: 'sigstore' })
-      .reply(200, { value: oidcToken })
-
-    const pool = mockAgent.get('https://api.github.com')
-    pool
-      .intercept({
-        path: /^\/repos\/.*\/.*\/attestations$/,
-        method: 'post'
-      })
-      .reply(201, { id: attestationID })
-
-    pool
-      .intercept({
-        path: /^\/orgs\/.*\/artifacts\/metadata\/storage-record$/,
-        method: 'post'
-      })
-      .reply(200, { storage_records: [{ id: storageRecordID }] })
-
-    process.env = {
-      ...originalEnv,
-      ACTIONS_ID_TOKEN_REQUEST_URL: tokenURL,
-      ACTIONS_ID_TOKEN_REQUEST_TOKEN: 'token',
-      RUNNER_TEMP: process.env.RUNNER_TEMP || '/tmp'
-    }
-  })
-
-  afterEach(() => {
-    // Restore the original environment
-    process.env = originalEnv
-
-    // Restore the original github.context
-    setGHContext(originalContext)
-  })
-
-  describe('when ACTIONS_ID_TOKEN_REQUEST_URL is not set', () => {
-    const inputs: RunInputs = {
-      ...defaultInputs,
-      subjectDigest,
-      subjectName,
-      predicateType,
-      predicate,
-      githubToken: 'gh-token'
-    }
-
-    beforeEach(() => {
-      // Nullify the OIDC token URL
-      process.env.ACTIONS_ID_TOKEN_REQUEST_URL = ''
-    })
-
-    it('sets a failed status', async () => {
-      await run(inputs)
-
-      expect(setFailedMock).toHaveBeenCalledWith(
-        new Error(
-          'missing "id-token" permission. Please add "permissions: id-token: write" to your workflow.'
-        )
-      )
-    })
-  })
-
-  describe('when no inputs are provided', () => {
-    it('sets a failed status', async () => {
-      await run(defaultInputs)
-
-      expect(setFailedMock).toHaveBeenCalledWith(
-        new Error(
-          'One of subject-path, subject-digest, or subject-checksums must be provided'
-        )
-      )
-    })
-  })
-
-  describe('when the repository is private', () => {
-    const inputs: RunInputs = {
-      ...defaultInputs,
-      subjectDigest,
-      subjectName,
-      predicateType,
-      predicate,
-      githubToken: 'gh-token'
-    }
-
-    beforeEach(async () => {
-      // Set the GH context with private repository visibility and a repo owner.
-      setGHContext({
-        payload: { repository: { visibility: 'private' } },
-        repo: { owner: 'foo', repo: 'bar' }
-      })
-
-      // Mock createAttestation to return expected values
-      createAttestationMock.mockResolvedValue({
-        attestationID,
-        certificate:
-          '-----BEGIN CERTIFICATE-----\ntest\n-----END CERTIFICATE-----',
-        tlogID: 'tlog-123',
-        attestationDigest: 'sha256:123456',
-        bundle: { mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json' }
-      })
-
-      await mockFulcio({
-        baseURL: 'https://fulcio.githubapp.com',
-        strict: false
-      })
-      await mockTSA({ baseURL: 'https://timestamp.githubapp.com' })
-    })
-
-    it('invokes the action w/o error', async () => {
-      await run(inputs)
-
-      expect(setFailedMock).not.toHaveBeenCalled()
-      expect(infoMock).toHaveBeenCalledWith('Attestation type: Custom')
-      expect(infoMock).toHaveBeenCalledWith(
-        expect.stringMatching(
-          `Attestation created for ${subjectName}@${subjectDigest}`
-        )
-      )
-      expect(createAttestationMock).toHaveBeenCalled()
-    })
-  })
-
-  describe('when the repository is public', () => {
-    const inputs: RunInputs = {
-      ...defaultInputs,
-      subjectDigest,
-      subjectName,
-      predicateType,
-      predicate,
-      githubToken: 'gh-token',
-      pushToRegistry: true
-    }
-
-    beforeEach(async () => {
-      // Set the GH context with public repository visibility and a repo owner.
-      setGHContext({
-        payload: { repository: { visibility: 'public' } },
-        repo: { owner: 'foo', repo: 'bar' }
-      })
-
-      // Setup createAttestation mock
-      createAttestationMock.mockResolvedValue({
-        attestationID,
-        certificate:
-          '-----BEGIN CERTIFICATE-----\ntest\n-----END CERTIFICATE-----',
-        tlogID: 'tlog-123',
-        attestationDigest: 'sha256:123456',
-        bundle: { mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json' },
-        storageRecordIds: [storageRecordID]
-      })
-
-      await mockFulcio({
-        baseURL: 'https://fulcio.sigstore.dev',
-        strict: false
-      })
-      await mockRekor({ baseURL: 'https://rekor.sigstore.dev' })
-
-      mockGetOctokit.mockReturnValue({
-        rest: {
-          repos: {
-            get: jest
-              .fn<() => Promise<{ data: { owner: { type: string } } }>>()
-              .mockResolvedValue({
-                data: { owner: { type: 'Organization' } }
-              })
-          }
-        }
-      })
-    })
-
-    it('invokes the action w/o error', async () => {
-      await run(inputs)
-
-      expect(setFailedMock).not.toHaveBeenCalled()
-      expect(createAttestationMock).toHaveBeenCalled()
-      expect(infoMock).toHaveBeenCalledWith('Attestation type: Custom')
-      expect(infoMock).toHaveBeenCalledWith(
-        expect.stringMatching(
-          `Attestation created for ${subjectName}@${subjectDigest}`
-        )
-      )
-    })
-
-    it('catches error when storage record creation fails and continues', async () => {
-      // Mock createAttestation to simulate storage record failure (but still succeed overall)
-      createAttestationMock.mockResolvedValue({
-        attestationID,
-        certificate:
-          '-----BEGIN CERTIFICATE-----\ntest\n-----END CERTIFICATE-----',
-        tlogID: 'tlog-123',
-        attestationDigest: 'sha256:123456',
-        bundle: { mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json' }
-        // No storageRecordIDs - simulates empty/failed storage record
-      })
-
-      await run(inputs)
-
-      expect(createAttestationMock).toHaveBeenCalled()
-      expect(setFailedMock).not.toHaveBeenCalled()
-    })
-
-    it('does not create a storage record when the repo is owned by a user', async () => {
-      // Mock createAttestation to not return storage record IDs
-      createAttestationMock.mockResolvedValue({
-        attestationID,
-        certificate:
-          '-----BEGIN CERTIFICATE-----\ntest\n-----END CERTIFICATE-----',
-        tlogID: 'tlog-123',
-        attestationDigest: 'sha256:123456',
-        bundle: { mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json' }
-      })
-
-      await run(inputs)
-
-      expect(setFailedMock).not.toHaveBeenCalled()
-      expect(createAttestationMock).toHaveBeenCalled()
-      expect(infoMock).toHaveBeenCalledWith(
-        expect.stringMatching(
-          `Attestation created for ${subjectName}@${subjectDigest}`
-        )
-      )
-    })
-  })
-
-  describe('when the subject count is greater than 1', () => {
-    let dir = ''
-    const filename = 'subject'
-
-    beforeEach(async () => {
-      const subjectCount = 5
-      const content = 'file content'
-
-      // Set-up temp directory
-      const tmpDir = await fs.realpath(os.tmpdir())
-      dir = await fs.mkdtemp(tmpDir + path.sep)
-
-      // Add files for glob testing
-      for (let i = 0; i < subjectCount; i++) {
-        await fs.writeFile(path.join(dir, `${filename}-${i}`), content)
-      }
-
-      // Set the GH context with private repository visibility and a repo owner.
-      setGHContext({
-        payload: { repository: { visibility: 'private' } },
-        repo: { owner: 'foo', repo: 'bar' }
-      })
-
-      // Set-up a Fulcio mock for each subject
-      await mockFulcio({
-        baseURL: 'https://fulcio.githubapp.com',
-        strict: false
-      })
-
-      // Set-up a TSA mock for each subject
-      await mockTSA({ baseURL: 'https://timestamp.githubapp.com' })
-    })
-
-    afterEach(async () => {
-      // Clean-up temp directory
-      await fs.rm(dir, { recursive: true })
-    })
-
-    it('invokes the action w/o error', async () => {
-      const inputs: RunInputs = {
-        ...defaultInputs,
-        subjectPath: path.join(dir, `${filename}-*`),
-        predicateType,
-        predicate,
-        githubToken: 'gh-token'
-      }
-      await run(inputs)
-
-      expect(setFailedMock).not.toHaveBeenCalled()
-      expect(infoMock).toHaveBeenNthCalledWith(1, 'Attestation type: Custom')
-      expect(infoMock).toHaveBeenNthCalledWith(
-        2,
-        expect.stringMatching('Attestation created for 5 subjects')
-      )
-    })
-  })
-
-  describe('when the subject count exceeds the max', () => {
-    let dir = ''
-    const filename = 'subject'
-
-    beforeEach(async () => {
-      const subjectCount = 1025
-      const content = 'file content'
-
-      // Set-up temp directory
-      const tmpDir = await fs.realpath(os.tmpdir())
-      dir = await fs.mkdtemp(tmpDir + path.sep)
-
-      // Add files for glob testing
-      for (let i = 0; i < subjectCount; i++) {
-        await fs.writeFile(path.join(dir, `${filename}-${i}`), content)
-      }
-
-      // Set the GH context with private repository visibility and a repo owner.
-      setGHContext({
-        payload: { repository: { visibility: 'private' } },
-        repo: { owner: 'foo', repo: 'bar' }
-      })
-    })
-
-    afterEach(async () => {
-      // Clean-up temp directory
-      await fs.rm(dir, { recursive: true })
-    })
-
-    it('sets a failed status', async () => {
-      const inputs: RunInputs = {
-        ...defaultInputs,
-        subjectPath: path.join(dir, `${filename}-*`),
-        predicateType,
-        predicate,
-        githubToken: 'gh-token'
-      }
-      await run(inputs)
-
-      expect(setFailedMock).toHaveBeenCalledWith(
-        new Error(
-          'Too many subjects specified (>1024). The maximum number of subjects is 1024.'
-        )
-      )
-    })
-  })
-
-  describe('attestation type detection', () => {
-    describe('when sbom-path is provided with predicate inputs', () => {
-      it('sets a failed status for conflicting inputs', async () => {
-        const inputs: RunInputs = {
-          ...defaultInputs,
-          subjectDigest,
-          subjectName,
-          sbomPath: '/path/to/sbom.json',
-          predicateType: 'https://example.com/predicate',
-          githubToken: 'gh-token'
-        }
-
-        await run(inputs)
-
-        expect(setFailedMock).toHaveBeenCalledWith(
-          new Error(
-            'Cannot specify sbom-path together with predicate-type, predicate, or predicate-path'
-          )
-        )
-      })
-    })
-
-    describe('when predicate is provided without predicate-type', () => {
-      it('sets a failed status for missing predicate-type', async () => {
-        const inputs: RunInputs = {
-          ...defaultInputs,
-          subjectDigest,
-          subjectName,
-          predicate: '{}',
-          githubToken: 'gh-token'
-        }
-
-        await run(inputs)
-
-        expect(setFailedMock).toHaveBeenCalledWith(
-          new Error(
-            'predicate-type is required when using predicate or predicate-path'
-          )
-        )
-      })
-    })
-
-    describe('when custom attestation inputs are provided', () => {
-      const inputs: RunInputs = {
-        ...defaultInputs,
-        subjectDigest,
-        subjectName,
-        predicateType,
-        predicate,
-        githubToken: 'gh-token'
-      }
-
-      beforeEach(async () => {
-        setGHContext({
-          payload: { repository: { visibility: 'private' } },
-          repo: { owner: 'foo', repo: 'bar' }
-        })
-
-        await mockFulcio({
-          baseURL: 'https://fulcio.githubapp.com',
-          strict: false
-        })
-        await mockTSA({ baseURL: 'https://timestamp.githubapp.com' })
-      })
-
-      it('logs the attestation type as Custom', async () => {
-        await run(inputs)
-
-        expect(setFailedMock).not.toHaveBeenCalled()
-        expect(infoMock).toHaveBeenCalledWith('Attestation type: Custom')
-      })
-    })
-
-    describe('when provenance attestation is detected', () => {
-      const inputs: RunInputs = {
-        ...defaultInputs,
-        subjectDigest,
-        subjectName,
-        githubToken: 'gh-token'
-      }
-
-      const mockProvPredicate = {
-        type: 'https://slsa.dev/provenance/v1',
-        params: { buildDefinition: {}, runDetails: {} }
-      }
-
-      beforeEach(async () => {
-        // Configure mock for provenance predicate
-        generateProvenancePredicateMock.mockResolvedValue(mockProvPredicate)
-
-        // Configure mock for createAttestation
-        createAttestationMock.mockResolvedValue({
-          attestationID: '1234567890',
-          certificate:
-            '-----BEGIN CERTIFICATE-----\ntest\n-----END CERTIFICATE-----',
-          tlogID: 'tlog-123',
-          attestationDigest: 'sha256:123456',
-          bundle: { mediaType: 'application/vnd.dev.sigstore.bundle.v0.3+json' }
-        })
-
-        setGHContext({
-          payload: { repository: { visibility: 'private' } },
-          repo: { owner: 'foo', repo: 'bar' }
-        })
-
-        await mockFulcio({
-          baseURL: 'https://fulcio.githubapp.com',
-          strict: false
-        })
-        await mockTSA({ baseURL: 'https://timestamp.githubapp.com' })
-      })
-
-      it('logs the attestation type as Build Provenance and generates predicate', async () => {
-        await run(inputs)
-
-        expect(setFailedMock).not.toHaveBeenCalled()
-        expect(infoMock).toHaveBeenCalledWith(
-          'Attestation type: Build Provenance'
-        )
-      })
-    })
-
-    describe('when sbom attestation is detected', () => {
-      let tmpDir: string
-      let sbomFilePath: string
-
-      const spdxSBOM = {
-        spdxVersion: 'SPDX-2.3',
-        SPDXID: 'SPDXRef-DOCUMENT',
-        name: 'test-package',
-        packages: []
-      }
-
-      beforeEach(async () => {
-        tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), 'main-test-'))
-        sbomFilePath = path.join(tmpDir, 'sbom.spdx.json')
-        await fs.writeFile(sbomFilePath, JSON.stringify(spdxSBOM))
-
-        setGHContext({
-          payload: { repository: { visibility: 'private' } },
-          repo: { owner: 'foo', repo: 'bar' }
-        })
-
-        await mockFulcio({
-          baseURL: 'https://fulcio.githubapp.com',
-          strict: false
-        })
-        await mockTSA({ baseURL: 'https://timestamp.githubapp.com' })
-      })
-
-      afterEach(async () => {
-        await fs.rm(tmpDir, { recursive: true })
-      })
-
-      it('logs the attestation type as SBOM and generates predicate', async () => {
-        const inputs: RunInputs = {
-          ...defaultInputs,
-          subjectDigest,
-          subjectName,
-          sbomPath: sbomFilePath,
-          githubToken: 'gh-token'
-        }
-
-        await run(inputs)
-
-        expect(setFailedMock).not.toHaveBeenCalled()
-        expect(infoMock).toHaveBeenCalledWith('Attestation type: SBOM')
-      })
-    })
-  })
-})
-
-// Helper to update the mock context
-function setGHContext(context: {
-  repo?: { owner: string; repo: string }
-  payload?: { repository?: { visibility: string } }
-}): void {
-  if (context.repo) {
-    mockContext.repo = context.repo
-  }
-  if (context.payload) {
-    mockContext.payload = context.payload as typeof mockContext.payload
-  }
-}
diff --git a/__tests__/predicate.test.ts b/__tests__/predicate.test.ts
deleted file mode 100644
index 1a71fa6..0000000
--- a/__tests__/predicate.test.ts
+++ /dev/null
@@ -1,133 +0,0 @@
-import fs from 'fs/promises'
-import os from 'os'
-import path from 'path'
-import { predicateFromInputs, PredicateInputs } from '../src/predicate'
-
-describe('subjectFromInputs', () => {
-  const blankInputs: PredicateInputs = {
-    predicateType: '',
-    predicate: '',
-    predicatePath: ''
-  }
-
-  describe('when no inputs are provided', () => {
-    it('throws an error', async () => {
-      await expect(predicateFromInputs(blankInputs)).rejects.toThrow(
-        /predicate-type/i
-      )
-    })
-  })
-
-  describe('when neither predicate path nor predicate are provided', () => {
-    it('throws an error', async () => {
-      const inputs: PredicateInputs = {
-        ...blankInputs,
-        predicateType: 'https://example.com/predicate'
-      }
-
-      await expect(predicateFromInputs(inputs)).rejects.toThrow(
-        /one of predicate-path or predicate must be provided/i
-      )
-    })
-  })
-
-  describe('when both predicate path and predicate are provided', () => {
-    it('throws an error', async () => {
-      const inputs: PredicateInputs = {
-        predicateType: 'https://example.com/predicate',
-        predicate: '{}',
-        predicatePath: 'path/to/predicate'
-      }
-
-      await expect(predicateFromInputs(inputs)).rejects.toThrow(
-        /only one of predicate-path or predicate may be provided/i
-      )
-    })
-  })
-
-  describe('when specifying a predicate path', () => {
-    const predicateType = 'https://example.com/predicate'
-    const content = '{}'
-    let predicatePath = ''
-
-    beforeEach(async () => {
-      // Set-up temp directory
-      const tmpDir = await fs.realpath(os.tmpdir())
-      const dir = await fs.mkdtemp(tmpDir + path.sep)
-
-      const filename = 'subject'
-      predicatePath = path.join(dir, filename)
-
-      // Write file to temp directory
-      await fs.writeFile(predicatePath, content)
-    })
-
-    afterEach(async () => {
-      // Clean-up temp directory
-      await fs.rm(path.parse(predicatePath).dir, { recursive: true })
-    })
-
-    it('returns the predicate', async () => {
-      const inputs: PredicateInputs = {
-        ...blankInputs,
-        predicateType,
-        predicatePath
-      }
-      await expect(predicateFromInputs(inputs)).resolves.toEqual({
-        type: predicateType,
-        params: JSON.parse(content)
-      })
-    })
-  })
-
-  describe('when specifying a predicate path that does not exist', () => {
-    const predicateType = 'https://example.com/predicate'
-    const predicatePath = 'foo'
-
-    it('returns the predicate', async () => {
-      const inputs: PredicateInputs = {
-        ...blankInputs,
-        predicateType,
-        predicatePath
-      }
-      await expect(predicateFromInputs(inputs)).rejects.toThrow(
-        /file not found/
-      )
-    })
-  })
-
-  describe('when specifying a predicate value', () => {
-    const predicateType = 'https://example.com/predicate'
-    const content = '{}'
-
-    it('returns the predicate', async () => {
-      const inputs: PredicateInputs = {
-        ...blankInputs,
-        predicateType,
-        predicate: content
-      }
-
-      await expect(predicateFromInputs(inputs)).resolves.toEqual({
-        type: predicateType,
-        params: JSON.parse(content)
-      })
-    })
-  })
-
-  describe('when specifying a predicate value exceeding the max size', () => {
-    const predicateType = 'https://example.com/predicate'
-    const content = JSON.stringify({ a: 'a'.repeat(16 * 1024 * 1024) })
-
-    it('throws an error', async () => {
-      const inputs: PredicateInputs = {
-        ...blankInputs,
-        predicateType,
-        predicate: content
-      }
-
-      await expect(predicateFromInputs(inputs)).rejects.toThrow(
-        /predicate string exceeds maximum/
-      )
-    })
-  })
-})
diff --git a/__tests__/sbom.test.ts b/__tests__/sbom.test.ts
deleted file mode 100644
index 17b72d5..0000000
--- a/__tests__/sbom.test.ts
+++ /dev/null
@@ -1,161 +0,0 @@
-import fs from 'fs/promises'
-import os from 'os'
-import path from 'path'
-import { parseSBOMFromPath, generateSBOMPredicate, SBOM } from '../src/sbom'
-
-describe('parseSBOMFromPath', () => {
-  let tmpDir: string
-
-  beforeEach(async () => {
-    tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), 'sbom-test-'))
-  })
-
-  afterEach(async () => {
-    await fs.rm(tmpDir, { recursive: true })
-  })
-
-  describe('when file does not exist', () => {
-    it('throws an error', async () => {
-      await expect(parseSBOMFromPath('/nonexistent/file.json')).rejects.toThrow(
-        /SBOM file not found/
-      )
-    })
-  })
-
-  describe('when file contains valid SPDX SBOM', () => {
-    const spdxSBOM = {
-      spdxVersion: 'SPDX-2.3',
-      SPDXID: 'SPDXRef-DOCUMENT',
-      name: 'test-package',
-      packages: []
-    }
-
-    it('returns SBOM with type spdx', async () => {
-      const filePath = path.join(tmpDir, 'sbom.spdx.json')
-      await fs.writeFile(filePath, JSON.stringify(spdxSBOM))
-
-      const result = await parseSBOMFromPath(filePath)
-
-      expect(result.type).toBe('spdx')
-      expect(result.object).toEqual(spdxSBOM)
-    })
-  })
-
-  describe('when file contains valid CycloneDX SBOM', () => {
-    const cyclonedxSBOM = {
-      bomFormat: 'CycloneDX',
-      specVersion: '1.4',
-      serialNumber: 'urn:uuid:12345',
-      components: []
-    }
-
-    it('returns SBOM with type cyclonedx', async () => {
-      const filePath = path.join(tmpDir, 'sbom.cdx.json')
-      await fs.writeFile(filePath, JSON.stringify(cyclonedxSBOM))
-
-      const result = await parseSBOMFromPath(filePath)
-
-      expect(result.type).toBe('cyclonedx')
-      expect(result.object).toEqual(cyclonedxSBOM)
-    })
-  })
-
-  describe('when file contains invalid SBOM format', () => {
-    it('throws an error', async () => {
-      const filePath = path.join(tmpDir, 'invalid.json')
-      await fs.writeFile(filePath, JSON.stringify({ random: 'data' }))
-
-      await expect(parseSBOMFromPath(filePath)).rejects.toThrow(
-        /Unsupported SBOM format/
-      )
-    })
-  })
-
-  describe('when file contains invalid JSON', () => {
-    it('throws an error', async () => {
-      const filePath = path.join(tmpDir, 'invalid.json')
-      await fs.writeFile(filePath, 'not valid json')
-
-      await expect(parseSBOMFromPath(filePath)).rejects.toThrow()
-    })
-  })
-
-  describe('when file exceeds maximum size', () => {
-    it('throws an error', async () => {
-      const filePath = path.join(tmpDir, 'large.json')
-      // Create a file larger than 16MB
-      const largeContent = 'x'.repeat(17 * 1024 * 1024)
-      await fs.writeFile(filePath, largeContent)
-
-      await expect(parseSBOMFromPath(filePath)).rejects.toThrow(
-        /SBOM file exceeds maximum allowed size/
-      )
-    })
-  })
-})
-
-describe('generateSBOMPredicate', () => {
-  describe('for SPDX SBOM', () => {
-    const spdxSBOM: SBOM = {
-      type: 'spdx',
-      object: {
-        spdxVersion: 'SPDX-2.3',
-        SPDXID: 'SPDXRef-DOCUMENT',
-        name: 'test-package'
-      }
-    }
-
-    it('returns predicate with correct SPDX type', () => {
-      const predicate = generateSBOMPredicate(spdxSBOM)
-
-      expect(predicate.type).toBe('https://spdx.dev/Document/v2.3')
-      expect(predicate.params).toEqual(spdxSBOM.object)
-    })
-  })
-
-  describe('for CycloneDX SBOM', () => {
-    const cyclonedxSBOM: SBOM = {
-      type: 'cyclonedx',
-      object: {
-        bomFormat: 'CycloneDX',
-        specVersion: '1.4',
-        serialNumber: 'urn:uuid:12345'
-      }
-    }
-
-    it('returns predicate with correct CycloneDX type', () => {
-      const predicate = generateSBOMPredicate(cyclonedxSBOM)
-
-      expect(predicate.type).toBe('https://cyclonedx.org/bom')
-      expect(predicate.params).toEqual(cyclonedxSBOM.object)
-    })
-  })
-
-  describe('for SPDX without version', () => {
-    const invalidSBOM: SBOM = {
-      type: 'spdx',
-      object: {
-        SPDXID: 'SPDXRef-DOCUMENT'
-      }
-    }
-
-    it('throws an error', () => {
-      expect(() => generateSBOMPredicate(invalidSBOM)).toThrow(
-        /Cannot find spdxVersion/
-      )
-    })
-  })
-
-  describe('for unsupported SBOM type', () => {
-    const unsupportedSBOM = {
-      type: 'unknown' as SBOM['type'],
-      object: { foo: 'bar' }
-    }
-
-    it('throws an error', () => {
-      expect(() => generateSBOMPredicate(unsupportedSBOM)).toThrow(
-        /Unsupported SBOM format/
-      )
-    })
-  })
-})
diff --git a/__tests__/style.test.ts b/__tests__/style.test.ts
deleted file mode 100644
index d7ebe8f..0000000
--- a/__tests__/style.test.ts
+++ /dev/null
@@ -1,15 +0,0 @@
-import { highlight, mute } from '../src/style'
-
-describe('style', () => {
-  describe('highlight', () => {
-    it('adds cyan color to the string', () => {
-      expect(highlight('foo')).toBe('\x1B[36mfoo\x1B[39m')
-    })
-  })
-
-  describe('mute', () => {
-    it('adds gray color to the string', () => {
-      expect(mute('foo')).toBe('\x1B[38;5;244mfoo\x1B[39m')
-    })
-  })
-})
diff --git a/__tests__/subject.test.ts b/__tests__/subject.test.ts
deleted file mode 100644
index 7064a00..0000000
--- a/__tests__/subject.test.ts
+++ /dev/null
@@ -1,600 +0,0 @@
-import crypto from 'crypto'
-import fs from 'fs/promises'
-import os from 'os'
-import path from 'path'
-import {
-  formatSubjectDigest,
-  subjectFromInputs,
-  SubjectInputs
-} from '../src/subject'
-
-describe('subjectFromInputs', () => {
-  const blankInputs: SubjectInputs = {
-    subjectPath: '',
-    subjectName: '',
-    subjectDigest: '',
-    subjectChecksums: ''
-  }
-
-  describe('when no inputs are provided', () => {
-    it('throws an error', async () => {
-      await expect(subjectFromInputs(blankInputs)).rejects.toThrow(
-        /one of subject-path, subject-digest, or subject-checksums must be provided/i
-      )
-    })
-  })
-
-  describe('when both subject path and subject digest are provided', () => {
-    it('throws an error', async () => {
-      const inputs: SubjectInputs = {
-        subjectName: 'foo',
-        subjectPath: 'path/to/subject',
-        subjectDigest: 'digest',
-        subjectChecksums: ''
-      }
-
-      await expect(subjectFromInputs(inputs)).rejects.toThrow(
-        /only one of subject-path, subject-digest, or subject-checksums may be provided/i
-      )
-    })
-  })
-
-  describe('when both subject path and subject checksums are provided', () => {
-    it('throws an error', async () => {
-      const inputs: SubjectInputs = {
-        subjectName: '',
-        subjectPath: 'path/to/subject',
-        subjectDigest: '',
-        subjectChecksums: 'path/to/checksums'
-      }
-
-      await expect(subjectFromInputs(inputs)).rejects.toThrow(
-        /only one of subject-path, subject-digest, or subject-checksums may be provided/i
-      )
-    })
-  })
-
-  describe('when both subject digest and subject checksums are provided', () => {
-    it('throws an error', async () => {
-      const inputs: SubjectInputs = {
-        subjectName: 'foo',
-        subjectPath: '',
-        subjectDigest: 'digest',
-        subjectChecksums: 'path/to/checksums'
-      }
-
-      await expect(subjectFromInputs(inputs)).rejects.toThrow(
-        /only one of subject-path, subject-digest, or subject-checksums may be provided/i
-      )
-    })
-  })
-
-  describe('when subject digest is provided but not the name', () => {
-    it('throws an error', async () => {
-      const inputs: SubjectInputs = {
-        ...blankInputs,
-        subjectDigest: 'digest'
-      }
-
-      await expect(subjectFromInputs(inputs)).rejects.toThrow(
-        /subject-name must be provided when using subject-digest/i
-      )
-    })
-  })
-
-  describe('when specifying a subject digest', () => {
-    const name = 'Subject'
-
-    describe('when the digest is malformed', () => {
-      it('throws an error', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectDigest: 'digest',
-          subjectName: name
-        }
-
-        await expect(subjectFromInputs(inputs)).rejects.toThrow(
-          /subject-digest must be in the format "sha256:<hex-digest>"/i
-        )
-      })
-    })
-
-    describe('when the algorithm is not supported', () => {
-      it('throws an error', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectDigest: 'md5:deadbeef',
-          subjectName: name
-        }
-
-        await expect(subjectFromInputs(inputs)).rejects.toThrow(
-          /subject-digest must be in the format "sha256:<hex-digest>"/i
-        )
-      })
-    })
-
-    describe('when the sha256 digest is malformed', () => {
-      it('throws an error', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectDigest: 'sha256:deadbeef',
-          subjectName: name
-        }
-
-        await expect(subjectFromInputs(inputs)).rejects.toThrow(
-          /subject-digest must be in the format "sha256:<hex-digest>"/i
-        )
-      })
-    })
-
-    describe('when the sha256 digest is valid', () => {
-      const alg = 'sha256'
-      const digest =
-        '7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32'
-
-      it('returns the subject', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectDigest: `${alg}:${digest}`,
-          subjectName: name
-        }
-
-        const subject = await subjectFromInputs(inputs)
-
-        expect(subject).toBeDefined()
-        expect(subject).toHaveLength(1)
-        expect(subject[0].name).toEqual(name)
-        expect(subject[0].digest).toEqual({ [alg]: digest })
-      })
-    })
-
-    describe('when the downcaseName is true', () => {
-      const imageName = 'ghcr.io/FOO/bar'
-      const alg = 'sha256'
-      const digest =
-        '7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32'
-
-      it('returns the subject (with name downcased)', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectDigest: `${alg}:${digest}`,
-          subjectName: imageName,
-          downcaseName: true
-        }
-
-        const subject = await subjectFromInputs(inputs)
-
-        expect(subject).toBeDefined()
-        expect(subject).toHaveLength(1)
-        expect(subject[0].name).toEqual(imageName.toLowerCase())
-        expect(subject[0].digest).toEqual({ [alg]: digest })
-      })
-    })
-  })
-
-  describe('when specifying a subject path', () => {
-    describe('when the file does NOT exist', () => {
-      it('throws an error', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectPath: '/f/a/k/e'
-        }
-
-        await expect(subjectFromInputs(inputs)).rejects.toThrow(
-          /could not find subject at path/i
-        )
-      })
-    })
-  })
-
-  describe('when the file exists', () => {
-    let dir = ''
-    const filename = 'subject'
-    const content = 'file content'
-
-    const expectedDigest = crypto
-      .createHash('sha256')
-      .update(content)
-      .digest('hex')
-
-    beforeEach(async () => {
-      // Set-up temp directory
-      const tmpDir = await fs.realpath(os.tmpdir())
-      dir = await fs.mkdtemp(tmpDir + path.sep)
-
-      // Write file to temp directory
-      await fs.writeFile(path.join(dir, filename), content)
-
-      // Add files for glob testing
-      for (let i = 0; i < 3; i++) {
-        await fs.writeFile(path.join(dir, `${filename}-${i}`), content)
-        await fs.writeFile(path.join(dir, `other-${i}`), content)
-      }
-    })
-
-    afterEach(async () => {
-      // Clean-up temp directory
-      await fs.rm(dir, { recursive: true })
-    })
-
-    describe('when no name is provided', () => {
-      it('returns the subject', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectPath: path.join(dir, filename)
-        }
-
-        const subject = await subjectFromInputs(inputs)
-
-        expect(subject).toBeDefined()
-        expect(subject).toHaveLength(1)
-        expect(subject[0].name).toEqual(filename)
-        expect(subject[0].digest).toEqual({ sha256: expectedDigest })
-      })
-    })
-
-    describe('when a name is provided', () => {
-      const name = 'mysubject'
-
-      it('returns the subject', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectPath: path.join(dir, filename),
-          subjectName: name
-        }
-
-        const subject = await subjectFromInputs(inputs)
-
-        expect(subject).toBeDefined()
-        expect(subject).toHaveLength(1)
-        expect(subject[0].name).toEqual(name)
-        expect(subject[0].digest).toEqual({ sha256: expectedDigest })
-      })
-    })
-
-    describe('when a file glob is supplied', () => {
-      it('returns the multiple subjects', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectPath: path.join(dir, 'subject-*')
-        }
-
-        const subjects = await subjectFromInputs(inputs)
-
-        expect(subjects).toBeDefined()
-        expect(subjects).toHaveLength(3)
-
-        subjects.forEach((subject, i) => {
-          expect(subject.name).toEqual(`${filename}-${i}`)
-          expect(subject.digest).toEqual({ sha256: expectedDigest })
-        })
-      })
-    })
-
-    describe('when a file glob is supplied which also matches non-files', () => {
-      it('returns the subjects (excluding non-files)', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectPath: `${dir}*`
-        }
-
-        const subjects = await subjectFromInputs(inputs)
-
-        expect(subjects).toBeDefined()
-        expect(subjects).toHaveLength(7)
-      })
-    })
-
-    describe('when a comma-separated list is supplied', () => {
-      it('returns the multiple subjects', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectPath: `${path.join(dir, 'subject-1')},${path.join(dir, 'subject-2')}`
-        }
-
-        const subjects = await subjectFromInputs(inputs)
-
-        expect(subjects).toBeDefined()
-        expect(subjects).toHaveLength(2)
-
-        expect(subjects).toContainEqual({
-          name: 'subject-1',
-          digest: { sha256: expectedDigest }
-        })
-        expect(subjects).toContainEqual({
-          name: 'subject-2',
-          digest: { sha256: expectedDigest }
-        })
-      })
-    })
-
-    describe('when a multi-line list is supplied', () => {
-      it('returns the multiple subjects', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectPath: `${path.join(dir, 'subject-0')}\n${path.join(dir, 'subject-2')}`
-        }
-
-        const subjects = await subjectFromInputs(inputs)
-
-        expect(subjects).toBeDefined()
-        expect(subjects).toHaveLength(2)
-
-        expect(subjects).toContainEqual({
-          name: 'subject-0',
-          digest: { sha256: expectedDigest }
-        })
-        expect(subjects).toContainEqual({
-          name: 'subject-2',
-          digest: { sha256: expectedDigest }
-        })
-      })
-    })
-
-    describe('when an excluding glob is supplied', () => {
-      it('returns the multiple subjects', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectPath: `${path.join(dir, 'subject-*')},!${path.join(dir, 'subject-1')}`
-        }
-
-        const subjects = await subjectFromInputs(inputs)
-
-        expect(subjects).toBeDefined()
-        expect(subjects).toHaveLength(2)
-
-        expect(subjects).toContainEqual({
-          name: 'subject-0',
-          digest: { sha256: expectedDigest }
-        })
-        expect(subjects).toContainEqual({
-          name: 'subject-2',
-          digest: { sha256: expectedDigest }
-        })
-      })
-    })
-
-    describe('when a multi-line glob list is supplied', () => {
-      it('returns the multiple subjects', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectPath: `${path.join(dir, 'subject-*')}\n  ${path.join(dir, 'other-*')} `
-        }
-
-        const subjects = await subjectFromInputs(inputs)
-
-        expect(subjects).toBeDefined()
-        expect(subjects).toHaveLength(6)
-
-        expect(subjects).toContainEqual({
-          name: 'subject-0',
-          digest: { sha256: expectedDigest }
-        })
-        expect(subjects).toContainEqual({
-          name: 'subject-1',
-          digest: { sha256: expectedDigest }
-        })
-        expect(subjects).toContainEqual({
-          name: 'subject-2',
-          digest: { sha256: expectedDigest }
-        })
-
-        expect(subjects).toContainEqual({
-          name: 'other-0',
-          digest: { sha256: expectedDigest }
-        })
-        expect(subjects).toContainEqual({
-          name: 'other-1',
-          digest: { sha256: expectedDigest }
-        })
-        expect(subjects).toContainEqual({
-          name: 'other-2',
-          digest: { sha256: expectedDigest }
-        })
-      })
-    })
-
-    describe('when duplicate subjects are supplied', () => {
-      let otherDir = ''
-
-      // Add duplicate subject in alternate directory
-      beforeEach(async () => {
-        // Set-up temp directory
-        const tmpDir = await fs.realpath(os.tmpdir())
-        otherDir = await fs.mkdtemp(tmpDir + path.sep)
-
-        // Write file to temp directory
-        await fs.writeFile(path.join(otherDir, filename), content)
-      })
-
-      it('returns de-duplicated subjects', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectPath: `${path.join(dir, 'subject')}, ${path.join(otherDir, 'subject')} `
-        }
-        const subjects = await subjectFromInputs(inputs)
-
-        expect(subjects).toBeDefined()
-        expect(subjects).toHaveLength(1)
-      })
-    })
-  })
-
-  describe('when specifying a subject checksums file', () => {
-    const checksums = `
-187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d  demo_0.0.1_linux_amd64
-badline
-5d8b4751ef31f9440d843fcfa4e53ca2e25b1cb1f13fd355fdc7c24b41fe645293291ea9297ba3989078abb77ebbaac66be073618a9e4974dbd0361881d4c718 demo_0.0.1_darwin_arm64`
-
-    let dir = ''
-    const filename = 'checksums'
-
-    beforeEach(async () => {
-      // Set-up temp directory
-      const tmpDir = await fs.realpath(os.tmpdir())
-      dir = await fs.mkdtemp(tmpDir + path.sep)
-
-      // Write file to temp directory
-      await fs.writeFile(path.join(dir, filename), checksums)
-    })
-
-    afterEach(async () => {
-      // Clean-up temp directory
-      await fs.rm(dir, { recursive: true })
-    })
-
-    describe('when the specified path is NOT a file', () => {
-      it('throws an error', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectChecksums: dir
-        }
-        await expect(subjectFromInputs(inputs)).rejects.toThrow(
-          /subject checksums file not found/i
-        )
-      })
-    })
-
-    describe('when the specific path is a file', () => {
-      it('returns the multiple subjects', async () => {
-        const inputs: SubjectInputs = {
-          ...blankInputs,
-          subjectChecksums: path.join(dir, filename)
-        }
-        const subjects = await subjectFromInputs(inputs)
-
-        expect(subjects).toBeDefined()
-        expect(subjects).toHaveLength(2)
-
-        expect(subjects).toContainEqual({
-          name: 'demo_0.0.1_linux_amd64',
-          digest: {
-            sha256:
-              '187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d'
-          }
-        })
-        expect(subjects).toContainEqual({
-          name: 'demo_0.0.1_darwin_arm64',
-          digest: {
-            sha512:
-              '5d8b4751ef31f9440d843fcfa4e53ca2e25b1cb1f13fd355fdc7c24b41fe645293291ea9297ba3989078abb77ebbaac66be073618a9e4974dbd0361881d4c718'
-          }
-        })
-      })
-    })
-  })
-
-  describe('when specifying a subject checksums string', () => {
-    const checksums = `
-f861e68a080799ca83104630b56abb90d8dbcc5f8b5a8639cb691e269838f29e  demo_0.0.1_linux_386
-187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d *demo_0.0.1_linux_amd64
-9ecbf449e286a8a8748c161c52aa28b6b2fc64ab86f94161c5d1b3abc18156c5 demo_0.0.1_linux_arm64`
-
-    it('returns the multiple subjects', async () => {
-      const inputs: SubjectInputs = {
-        ...blankInputs,
-        subjectChecksums: checksums
-      }
-      const subjects = await subjectFromInputs(inputs)
-
-      expect(subjects).toBeDefined()
-      expect(subjects).toHaveLength(3)
-
-      expect(subjects).toContainEqual({
-        name: 'demo_0.0.1_linux_386',
-        digest: {
-          sha256:
-            'f861e68a080799ca83104630b56abb90d8dbcc5f8b5a8639cb691e269838f29e'
-        }
-      })
-      expect(subjects).toContainEqual({
-        name: 'demo_0.0.1_linux_amd64',
-        digest: {
-          sha256:
-            '187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d'
-        }
-      })
-      expect(subjects).toContainEqual({
-        name: 'demo_0.0.1_linux_arm64',
-        digest: {
-          sha256:
-            '9ecbf449e286a8a8748c161c52aa28b6b2fc64ab86f94161c5d1b3abc18156c5'
-        }
-      })
-    })
-  })
-
-  describe('when specifying a subject checksums string with duplicates', () => {
-    const checksums = `
-f861e68a080799ca83104630b56abb90d8dbcc5f8b5a8639cb691e269838f29e  demo_0.0.1_linux_386
-f861e68a080799ca83104630b56abb90d8dbcc5f8b5a8639cb691e269838f29e  demo_0.0.1_linux_386
-187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d *demo_0.0.1_linux_amd64`
-
-    it('returns de-duplicated subjects', async () => {
-      const inputs: SubjectInputs = {
-        ...blankInputs,
-        subjectChecksums: checksums
-      }
-      const subjects = await subjectFromInputs(inputs)
-
-      expect(subjects).toBeDefined()
-      expect(subjects).toHaveLength(2)
-
-      expect(subjects).toContainEqual({
-        name: 'demo_0.0.1_linux_386',
-        digest: {
-          sha256:
-            'f861e68a080799ca83104630b56abb90d8dbcc5f8b5a8639cb691e269838f29e'
-        }
-      })
-      expect(subjects).toContainEqual({
-        name: 'demo_0.0.1_linux_amd64',
-        digest: {
-          sha256:
-            '187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d'
-        }
-      })
-    })
-  })
-
-  describe('when specifying a subject checksums string with an unrecognized digest', () => {
-    const checksums = `f861e  demo_0.0.1_linux_386`
-
-    it('throws an error', async () => {
-      const inputs: SubjectInputs = {
-        ...blankInputs,
-        subjectChecksums: checksums
-      }
-
-      await expect(subjectFromInputs(inputs)).rejects.toThrow(
-        /unknown digest algorithm/i
-      )
-    })
-  })
-
-  describe('when specifying a subject checksums string with an invalid digest', () => {
-    const checksums =
-      '!!!!e68a080799ca83104630b56abb90d8dbcc5f8b5a8639cb691e269838f29e  demo_0.0.1_linux_386'
-
-    it('throws an error', async () => {
-      const inputs: SubjectInputs = {
-        ...blankInputs,
-        subjectChecksums: checksums
-      }
-
-      await expect(subjectFromInputs(inputs)).rejects.toThrow(/invalid digest/i)
-    })
-  })
-})
-
-describe('subjectDigest', () => {
-  it('returns the digest', () => {
-    const subject = {
-      name: 'foo',
-      digest: { sha1: 'deadbeef' }
-    }
-
-    const digest = formatSubjectDigest(subject)
-    expect(digest).toEqual('sha1:deadbeef')
-  })
-})
diff --git a/__tests__/detect.test.ts b/__tests__/unit/detect.test.ts
similarity index 64%
rename from __tests__/detect.test.ts
rename to __tests__/unit/detect.test.ts
index 36f959c..4820996 100644
--- a/__tests__/detect.test.ts
+++ b/__tests__/unit/detect.test.ts
@@ -2,7 +2,7 @@ import {
   detectAttestationType,
   validateAttestationInputs,
   DetectionInputs
-} from '../src/detect'
+} from '../../src/detect'
 
 describe('detectAttestationType', () => {
   const blankInputs: DetectionInputs = {
@@ -12,14 +12,12 @@ describe('detectAttestationType', () => {
     predicatePath: ''
   }
 
-  describe('when no inputs are provided', () => {
-    it('returns provenance', () => {
-      expect(detectAttestationType(blankInputs)).toBe('provenance')
-    })
+  it('should return provenance when no inputs are provided', () => {
+    expect(detectAttestationType(blankInputs)).toBe('provenance')
   })
 
-  describe('when sbom-path is provided', () => {
-    it('returns sbom', () => {
+  describe('SBOM detection', () => {
+    it('should return sbom when sbom-path is provided', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         sbomPath: '/path/to/sbom.json'
@@ -27,7 +25,7 @@ describe('detectAttestationType', () => {
       expect(detectAttestationType(inputs)).toBe('sbom')
     })
 
-    it('returns sbom even when predicate inputs are also provided', () => {
+    it('should prioritize sbom over custom predicate inputs', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         sbomPath: '/path/to/sbom.json',
@@ -37,38 +35,32 @@ describe('detectAttestationType', () => {
     })
   })
 
-  describe('when predicate-type is provided', () => {
-    it('returns custom', () => {
+  describe('custom detection', () => {
+    it('should return custom when predicate-type is provided', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         predicateType: 'https://example.com/predicate'
       }
       expect(detectAttestationType(inputs)).toBe('custom')
     })
-  })
 
-  describe('when predicate is provided', () => {
-    it('returns custom', () => {
+    it('should return custom when predicate is provided', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         predicate: '{}'
       }
       expect(detectAttestationType(inputs)).toBe('custom')
     })
-  })
 
-  describe('when predicate-path is provided', () => {
-    it('returns custom', () => {
+    it('should return custom when predicate-path is provided', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         predicatePath: '/path/to/predicate.json'
       }
       expect(detectAttestationType(inputs)).toBe('custom')
     })
-  })
 
-  describe('when predicate-type and predicate are provided', () => {
-    it('returns custom', () => {
+    it('should return custom when predicate-type and predicate are both provided', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         predicateType: 'https://example.com/predicate',
@@ -87,24 +79,20 @@ describe('validateAttestationInputs', () => {
     predicatePath: ''
   }
 
-  describe('when no inputs are provided', () => {
-    it('does not throw', () => {
-      expect(() => validateAttestationInputs(blankInputs)).not.toThrow()
-    })
+  it('should not throw when no inputs are provided', () => {
+    expect(() => validateAttestationInputs(blankInputs)).not.toThrow()
   })
 
-  describe('when sbom-path is provided alone', () => {
-    it('does not throw', () => {
-      const inputs: DetectionInputs = {
-        ...blankInputs,
-        sbomPath: '/path/to/sbom.json'
-      }
-      expect(() => validateAttestationInputs(inputs)).not.toThrow()
-    })
+  it('should not throw when sbom-path is provided alone', () => {
+    const inputs: DetectionInputs = {
+      ...blankInputs,
+      sbomPath: '/path/to/sbom.json'
+    }
+    expect(() => validateAttestationInputs(inputs)).not.toThrow()
   })
 
-  describe('when sbom-path is combined with predicate-type', () => {
-    it('throws an error', () => {
+  describe('sbom-path conflicts', () => {
+    it('should throw when sbom-path is combined with predicate-type', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         sbomPath: '/path/to/sbom.json',
@@ -114,10 +102,8 @@ describe('validateAttestationInputs', () => {
         /Cannot specify sbom-path together with/
       )
     })
-  })
 
-  describe('when sbom-path is combined with predicate', () => {
-    it('throws an error', () => {
+    it('should throw when sbom-path is combined with predicate', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         sbomPath: '/path/to/sbom.json',
@@ -127,10 +113,8 @@ describe('validateAttestationInputs', () => {
         /Cannot specify sbom-path together with/
       )
     })
-  })
 
-  describe('when sbom-path is combined with predicate-path', () => {
-    it('throws an error', () => {
+    it('should throw when sbom-path is combined with predicate-path', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         sbomPath: '/path/to/sbom.json',
@@ -142,8 +126,8 @@ describe('validateAttestationInputs', () => {
     })
   })
 
-  describe('when predicate is provided without predicate-type', () => {
-    it('throws an error', () => {
+  describe('predicate-type requirements', () => {
+    it('should throw when predicate is provided without predicate-type', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         predicate: '{}'
@@ -152,10 +136,8 @@ describe('validateAttestationInputs', () => {
         /predicate-type is required/
       )
     })
-  })
 
-  describe('when predicate-path is provided without predicate-type', () => {
-    it('throws an error', () => {
+    it('should throw when predicate-path is provided without predicate-type', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         predicatePath: '/path/to/predicate.json'
@@ -164,10 +146,8 @@ describe('validateAttestationInputs', () => {
         /predicate-type is required/
       )
     })
-  })
 
-  describe('when predicate-type and predicate are provided', () => {
-    it('does not throw', () => {
+    it('should not throw when predicate-type and predicate are provided', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         predicateType: 'https://example.com/predicate',
@@ -175,10 +155,8 @@ describe('validateAttestationInputs', () => {
       }
       expect(() => validateAttestationInputs(inputs)).not.toThrow()
     })
-  })
 
-  describe('when predicate-type and predicate-path are provided', () => {
-    it('does not throw', () => {
+    it('should not throw when predicate-type and predicate-path are provided', () => {
       const inputs: DetectionInputs = {
         ...blankInputs,
         predicateType: 'https://example.com/predicate',
diff --git a/__tests__/unit/predicate.test.ts b/__tests__/unit/predicate.test.ts
new file mode 100644
index 0000000..6d08b8b
--- /dev/null
+++ b/__tests__/unit/predicate.test.ts
@@ -0,0 +1,142 @@
+import fs from 'fs/promises'
+import os from 'os'
+import path from 'path'
+import { predicateFromInputs, PredicateInputs } from '../../src/predicate'
+
+describe('predicateFromInputs', () => {
+  const blankInputs: PredicateInputs = {
+    predicateType: '',
+    predicate: '',
+    predicatePath: ''
+  }
+
+  let tempDir: string
+
+  beforeEach(async () => {
+    tempDir = await fs.mkdtemp(path.join(os.tmpdir(), 'predicate-test-'))
+  })
+
+  afterEach(async () => {
+    await fs.rm(tempDir, { recursive: true, force: true })
+  })
+
+  describe('input validation', () => {
+    it('should throw when predicate-type is not provided', async () => {
+      await expect(predicateFromInputs(blankInputs)).rejects.toThrow(
+        /predicate-type must be provided/
+      )
+    })
+
+    it('should throw when neither predicate nor predicate-path is provided', async () => {
+      const inputs: PredicateInputs = {
+        ...blankInputs,
+        predicateType: 'https://example.com/predicate'
+      }
+      await expect(predicateFromInputs(inputs)).rejects.toThrow(
+        /one of predicate-path or predicate must be provided/i
+      )
+    })
+
+    it('should throw when both predicate and predicate-path are provided', async () => {
+      const inputs: PredicateInputs = {
+        predicateType: 'https://example.com/predicate',
+        predicate: '{}',
+        predicatePath: '/path/to/predicate.json'
+      }
+      await expect(predicateFromInputs(inputs)).rejects.toThrow(
+        /only one of predicate-path or predicate may be provided/i
+      )
+    })
+  })
+
+  describe('with predicate string', () => {
+    it('should parse and return the predicate', async () => {
+      const predicateType = 'https://example.com/predicate'
+      const predicateContent = { foo: 'bar', nested: { value: 123 } }
+
+      const inputs: PredicateInputs = {
+        ...blankInputs,
+        predicateType,
+        predicate: JSON.stringify(predicateContent)
+      }
+
+      const result = await predicateFromInputs(inputs)
+
+      expect(result).toEqual({
+        type: predicateType,
+        params: predicateContent
+      })
+    })
+
+    it('should throw when predicate string exceeds max size', async () => {
+      const predicateType = 'https://example.com/predicate'
+      const largeContent = JSON.stringify({ data: 'x'.repeat(16 * 1024 * 1024) })
+
+      const inputs: PredicateInputs = {
+        ...blankInputs,
+        predicateType,
+        predicate: largeContent
+      }
+
+      await expect(predicateFromInputs(inputs)).rejects.toThrow(
+        /predicate string exceeds maximum/
+      )
+    })
+
+    it('should throw when predicate is invalid JSON', async () => {
+      const inputs: PredicateInputs = {
+        ...blankInputs,
+        predicateType: 'https://example.com/predicate',
+        predicate: 'not valid json'
+      }
+
+      await expect(predicateFromInputs(inputs)).rejects.toThrow(/JSON/)
+    })
+  })
+
+  describe('with predicate path', () => {
+    it('should read and parse predicate from file', async () => {
+      const predicateType = 'https://example.com/predicate'
+      const predicateContent = { buildType: 'test', metadata: { version: '1.0' } }
+      const filePath = path.join(tempDir, 'predicate.json')
+
+      await fs.writeFile(filePath, JSON.stringify(predicateContent))
+
+      const inputs: PredicateInputs = {
+        ...blankInputs,
+        predicateType,
+        predicatePath: filePath
+      }
+
+      const result = await predicateFromInputs(inputs)
+
+      expect(result).toEqual({
+        type: predicateType,
+        params: predicateContent
+      })
+    })
+
+    it('should throw when predicate file does not exist', async () => {
+      const inputs: PredicateInputs = {
+        ...blankInputs,
+        predicateType: 'https://example.com/predicate',
+        predicatePath: '/nonexistent/file.json'
+      }
+
+      await expect(predicateFromInputs(inputs)).rejects.toThrow(/file not found/)
+    })
+
+    it('should throw when predicate file contains invalid JSON', async () => {
+      const filePath = path.join(tempDir, 'invalid.json')
+      await fs.writeFile(filePath, 'not valid json')
+
+      const inputs: PredicateInputs = {
+        ...blankInputs,
+        predicateType: 'https://example.com/predicate',
+        predicatePath: filePath
+      }
+
+      await expect(predicateFromInputs(inputs)).rejects.toThrow(/JSON/)
+    })
+  })
+})
diff --git a/__tests__/unit/sbom.test.ts b/__tests__/unit/sbom.test.ts
new file mode 100644
index 0000000..39613a5
--- /dev/null
+++ b/__tests__/unit/sbom.test.ts
@@ -0,0 +1,181 @@
+import { jest } from '@jest/globals'
+import fs from 'fs/promises'
+import os from 'os'
+import path from 'path'
+import { parseSBOMFromPath, generateSBOMPredicate, SBOM } from '../../src/sbom'
+
+describe('parseSBOMFromPath', () => {
+  let tempDir: string
+
+  beforeEach(async () => {
+    tempDir = await fs.mkdtemp(path.join(os.tmpdir(), 'sbom-test-'))
+  })
+
+  afterEach(async () => {
+    await fs.rm(tempDir, { recursive: true, force: true })
+  })
+
+  describe('file handling', () => {
+    it('should throw when file does not exist', async () => {
+      await expect(parseSBOMFromPath('/nonexistent/file.json')).rejects.toThrow(
+        /SBOM file not found/
+      )
+    })
+
+    it('should rethrow non-ENOENT errors', async () => {
+      const statSpy = jest.spyOn(fs, 'stat').mockRejectedValueOnce(
+        Object.assign(new Error('Permission denied'), { code: 'EACCES' })
+      )
+
+      await expect(parseSBOMFromPath('/some/file.json')).rejects.toThrow(
+        /Permission denied/
+      )
+
+      statSpy.mockRestore()
+    })
+
+    it('should throw when file contains invalid JSON', async () => {
+      const filePath = path.join(tempDir, 'invalid.json')
+      await fs.writeFile(filePath, 'not valid json')
+
+      await expect(parseSBOMFromPath(filePath)).rejects.toThrow(/JSON/)
+    })
+
+    it('should throw when file exceeds maximum size', async () => {
+      const filePath = path.join(tempDir, 'large.json')
+      const largeContent = 'x'.repeat(17 * 1024 * 1024)
+      await fs.writeFile(filePath, largeContent)
+
+      await expect(parseSBOMFromPath(filePath)).rejects.toThrow(
+        /SBOM file exceeds maximum allowed size/
+      )
+    })
+  })
+
+  describe('SPDX format', () => {
+    const spdxSBOM = {
+      spdxVersion: 'SPDX-2.3',
+      SPDXID: 'SPDXRef-DOCUMENT',
+      name: 'test-package',
+      packages: []
+    }
+
+    it('should parse valid SPDX SBOM', async () => {
+      const filePath = path.join(tempDir, 'sbom.spdx.json')
+      await fs.writeFile(filePath, JSON.stringify(spdxSBOM))
+
+      const result = await parseSBOMFromPath(filePath)
+
+      expect(result.type).toBe('spdx')
+      expect(result.object).toEqual(spdxSBOM)
+    })
+  })
+
+  describe('CycloneDX format', () => {
+    const cyclonedxSBOM = {
+      bomFormat: 'CycloneDX',
+      specVersion: '1.4',
+      serialNumber: 'urn:uuid:12345',
+      components: []
+    }
+
+    it('should parse valid CycloneDX SBOM', async () => {
+      const filePath = path.join(tempDir, 'sbom.cdx.json')
+      await fs.writeFile(filePath, JSON.stringify(cyclonedxSBOM))
+
+      const result = await parseSBOMFromPath(filePath)
+
+      expect(result.type).toBe('cyclonedx')
+      expect(result.object).toEqual(cyclonedxSBOM)
+    })
+  })
+
+  describe('unsupported formats', () => {
+    it('should throw for unrecognized SBOM format', async () => {
+      const filePath = path.join(tempDir, 'invalid-sbom.json')
+      await fs.writeFile(filePath, JSON.stringify({ random: 'data' }))
+
+      await expect(parseSBOMFromPath(filePath)).rejects.toThrow(
+        /Unsupported SBOM format/
+      )
+    })
+
+    it('should throw for SPDX missing SPDXID', async () => {
+      const filePath = path.join(tempDir, 'partial-spdx.json')
+      await fs.writeFile(filePath, JSON.stringify({ spdxVersion: 'SPDX-2.3' }))
+
+      await expect(parseSBOMFromPath(filePath)).rejects.toThrow(
+        /Unsupported SBOM format/
+      )
+    })
+
+    it('should throw for CycloneDX missing required fields', async () => {
+      const filePath = path.join(tempDir, 'partial-cdx.json')
+      await fs.writeFile(filePath, JSON.stringify({ bomFormat: 'CycloneDX' }))
+
+      await expect(parseSBOMFromPath(filePath)).rejects.toThrow(
+        /Unsupported SBOM format/
+      )
+    })
+  })
+})
+
+describe('generateSBOMPredicate', () => {
+  describe('SPDX predicates', () => {
+    it('should generate predicate with correct SPDX type URL', () => {
+      const sbom: SBOM = {
+        type: 'spdx',
+        object: {
+          spdxVersion: 'SPDX-2.3',
+          SPDXID: 'SPDXRef-DOCUMENT',
+          name: 'test-package'
+        }
+      }
+
+      const predicate = generateSBOMPredicate(sbom)
+
+      expect(predicate.type).toBe('https://spdx.dev/Document/v2.3')
+      expect(predicate.params).toEqual(sbom.object)
+    })
+
+    it('should throw when spdxVersion is missing', () => {
+      const sbom: SBOM = {
+        type: 'spdx',
+        object: { SPDXID: 'SPDXRef-DOCUMENT' }
+      }
+
+      expect(() => generateSBOMPredicate(sbom)).toThrow(
+        /Cannot find spdxVersion/
+      )
+    })
+  })
+
+  describe('CycloneDX predicates', () => {
+    it('should generate predicate with correct CycloneDX type URL', () => {
+      const sbom: SBOM = {
+        type: 'cyclonedx',
+        object: {
+          bomFormat: 'CycloneDX',
+          specVersion: '1.4',
+          serialNumber: 'urn:uuid:12345'
+        }
+      }
+
+      const predicate = generateSBOMPredicate(sbom)
+
+      expect(predicate.type).toBe('https://cyclonedx.org/bom')
+      expect(predicate.params).toEqual(sbom.object)
+    })
+  })
+
+  describe('unsupported types', () => {
+    it('should throw for unsupported SBOM type', () => {
+      const sbom = {
+        type: 'unknown' as SBOM['type'],
+        object: { foo: 'bar' }
+      }
+
+      expect(() => generateSBOMPredicate(sbom)).toThrow(/Unsupported SBOM format/)
+    })
+  })
+})
diff --git a/__tests__/unit/style.test.ts b/__tests__/unit/style.test.ts
new file mode 100644
index 0000000..7271fc7
--- /dev/null
+++ b/__tests__/unit/style.test.ts
@@ -0,0 +1,27 @@
+import { highlight, mute } from '../../src/style'
+
+describe('style', () => {
+  describe('highlight', () => {
+    it('should wrap text with cyan ANSI color codes', () => {
+      const result = highlight('test message')
+      expect(result).toBe('\x1B[36mtest message\x1B[39m')
+    })
+
+    it('should handle empty strings', () => {
+      const result = highlight('')
+      expect(result).toBe('\x1B[36m\x1B[39m')
+    })
+  })
+
+  describe('mute', () => {
+    it('should wrap text with gray ANSI color codes', () => {
+      const result = mute('test message')
+      expect(result).toBe('\x1B[38;5;244mtest message\x1B[39m')
+    })
+
+    it('should handle empty strings', () => {
+      const result = mute('')
+      expect(result).toBe('\x1B[38;5;244m\x1B[39m')
+    })
+  })
+})
diff --git a/__tests__/unit/subject.test.ts b/__tests__/unit/subject.test.ts
new file mode 100644
index 0000000..ca3c9b9
--- /dev/null
+++ b/__tests__/unit/subject.test.ts
@@ -0,0 +1,462 @@
+import crypto from 'crypto'
+import fs from 'fs/promises'
+import os from 'os'
+import path from 'path'
+import {
+  subjectFromInputs,
+  formatSubjectDigest,
+  SubjectInputs
+} from '../../src/subject'
+
+describe('subjectFromInputs', () => {
+  const blankInputs: SubjectInputs = {
+    subjectPath: '',
+    subjectName: '',
+    subjectDigest: '',
+    subjectChecksums: ''
+  }
+
+  let tempDir: string
+
+  beforeEach(async () => {
+    tempDir = await fs.mkdtemp(path.join(os.tmpdir(), 'subject-test-'))
+  })
+
+  afterEach(async () => {
+    await fs.rm(tempDir, { recursive: true, force: true })
+  })
+
+  describe('input validation', () => {
+    it('should throw when no inputs are provided', async () => {
+      await expect(subjectFromInputs(blankInputs)).rejects.toThrow(
+        /one of subject-path, subject-digest, or subject-checksums must be provided/i
+      )
+    })
+
+    it('should throw when multiple subject inputs are provided', async () => {
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectPath: '/some/path',
+        subjectDigest: 'sha256:abc123'
+      }
+      await expect(subjectFromInputs(inputs)).rejects.toThrow(
+        /only one of subject-path, subject-digest, or subject-checksums may be provided/i
+      )
+    })
+
+    it('should throw when subject-digest is provided without subject-name', async () => {
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectDigest: 'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32'
+      }
+      await expect(subjectFromInputs(inputs)).rejects.toThrow(
+        /subject-name must be provided when using subject-digest/i
+      )
+    })
+  })
+
+  describe('with subject-digest', () => {
+    const validDigest = 'sha256:7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32'
+
+    it('should return subject with provided name and digest', async () => {
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectName: 'my-artifact',
+        subjectDigest: validDigest
+      }
+
+      const subjects = await subjectFromInputs(inputs)
+
+      expect(subjects).toHaveLength(1)
+      expect(subjects[0].name).toBe('my-artifact')
+      expect(subjects[0].digest).toEqual({
+        sha256: '7d070f6b64d9bcc530fe99cc21eaaa4b3c364e0b2d367d7735671fa202a03b32'
+      })
+    })
+
+    it('should lowercase name when downcaseName is true', async () => {
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectName: 'ghcr.io/FOO/Bar',
+        subjectDigest: validDigest,
+        downcaseName: true
+      }
+
+      const subjects = await subjectFromInputs(inputs)
+
+      expect(subjects[0].name).toBe('ghcr.io/foo/bar')
+    })
+
+    it('should throw for malformed digest format', async () => {
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectName: 'artifact',
+        subjectDigest: 'invalid-digest'
+      }
+
+      await expect(subjectFromInputs(inputs)).rejects.toThrow(
+        /subject-digest must be in the format/
+      )
+    })
+
+    it('should throw for unsupported hash algorithm', async () => {
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectName: 'artifact',
+        subjectDigest: 'md5:d41d8cd98f00b204e9800998ecf8427e'
+      }
+
+      await expect(subjectFromInputs(inputs)).rejects.toThrow(
+        /subject-digest must be in the format/
+      )
+    })
+
+    it('should throw for incorrect sha256 digest length', async () => {
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectName: 'artifact',
+        subjectDigest: 'sha256:deadbeef'
+      }
+
+      await expect(subjectFromInputs(inputs)).rejects.toThrow(
+        /subject-digest must be in the format/
+      )
+    })
+  })
+
+  describe('with subject-path', () => {
+    const fileContent = 'test file content'
+    const expectedDigest = crypto.createHash('sha256').update(fileContent).digest('hex')
+
+    it('should calculate digest from file', async () => {
+      const filePath = path.join(tempDir, 'artifact.bin')
+      await fs.writeFile(filePath, fileContent)
+
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectPath: filePath
+      }
+
+      const subjects = await subjectFromInputs(inputs)
+
+      expect(subjects).toHaveLength(1)
+      expect(subjects[0].name).toBe('artifact.bin')
+      expect(subjects[0].digest).toEqual({ sha256: expectedDigest })
+    })
+
+    it('should use provided name instead of filename', async () => {
+      const filePath = path.join(tempDir, 'artifact.bin')
+      await fs.writeFile(filePath, fileContent)
+
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectPath: filePath,
+        subjectName: 'custom-name'
+      }
+
+      const subjects = await subjectFromInputs(inputs)
+
+      expect(subjects[0].name).toBe('custom-name')
+    })
+
+    it('should throw when file does not exist', async () => {
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectPath: '/nonexistent/file'
+      }
+
+      await expect(subjectFromInputs(inputs)).rejects.toThrow(
+        /could not find subject at path/i
+      )
+    })
+
+    describe('glob patterns', () => {
+      beforeEach(async () => {
+        for (let i = 0; i < 3; i++) {
+          await fs.writeFile(path.join(tempDir, `file-${i}.txt`), fileContent)
+        }
+      })
+
+      it('should expand glob pattern to multiple subjects', async () => {
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectPath: path.join(tempDir, 'file-*.txt')
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects).toHaveLength(3)
+        expect(subjects.map(s => s.name).sort()).toEqual([
+          'file-0.txt',
+          'file-1.txt',
+          'file-2.txt'
+        ])
+      })
+
+      it('should handle comma-separated paths', async () => {
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectPath: `${path.join(tempDir, 'file-0.txt')},${path.join(tempDir, 'file-1.txt')}`
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects).toHaveLength(2)
+      })
+
+      it('should handle newline-separated paths', async () => {
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectPath: `${path.join(tempDir, 'file-0.txt')}\n${path.join(tempDir, 'file-2.txt')}`
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects).toHaveLength(2)
+      })
+
+      it('should support exclusion patterns', async () => {
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectPath: `${path.join(tempDir, 'file-*.txt')},!${path.join(tempDir, 'file-1.txt')}`
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects).toHaveLength(2)
+        expect(subjects.map(s => s.name)).not.toContain('file-1.txt')
+      })
+
+      it('should deduplicate subjects with same name and digest', async () => {
+        // Create another directory with same file
+        const otherDir = await fs.mkdtemp(path.join(os.tmpdir(), 'subject-dup-'))
+        await fs.writeFile(path.join(otherDir, 'file-0.txt'), fileContent)
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectPath: `${path.join(tempDir, 'file-0.txt')},${path.join(otherDir, 'file-0.txt')}`
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects).toHaveLength(1)
+
+        await fs.rm(otherDir, { recursive: true, force: true })
+      })
+    })
+
+    it('should exclude directories from glob results', async () => {
+      await fs.mkdir(path.join(tempDir, 'subdir'))
+      await fs.writeFile(path.join(tempDir, 'file.txt'), fileContent)
+
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectPath: path.join(tempDir, '*')
+      }
+
+      const subjects = await subjectFromInputs(inputs)
+
+      expect(subjects).toHaveLength(1)
+      expect(subjects[0].name).toBe('file.txt')
+    })
+
+    it('should throw when too many subjects are specified', async () => {
+      // Create 1025 files (exceeds MAX_SUBJECT_COUNT of 1024)
+      for (let i = 0; i < 1025; i++) {
+        await fs.writeFile(path.join(tempDir, `file-${i}.txt`), `content-${i}`)
+      }
+
+      const inputs: SubjectInputs = {
+        ...blankInputs,
+        subjectPath: path.join(tempDir, 'file-*.txt')
+      }
+
+      await expect(subjectFromInputs(inputs)).rejects.toThrow(/too many subjects/i)
+    })
+  })
+
+  describe('with subject-checksums', () => {
+    describe('from string', () => {
+      it('should parse sha256 checksums', async () => {
+        const checksums = `187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d  artifact-linux
+9ecbf449e286a8a8748c161c52aa28b6b2fc64ab86f94161c5d1b3abc18156c5  artifact-darwin`
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: checksums
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects).toHaveLength(2)
+        expect(subjects).toContainEqual({
+          name: 'artifact-linux',
+          digest: { sha256: '187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d' }
+        })
+        expect(subjects).toContainEqual({
+          name: 'artifact-darwin',
+          digest: { sha256: '9ecbf449e286a8a8748c161c52aa28b6b2fc64ab86f94161c5d1b3abc18156c5' }
+        })
+      })
+
+      it('should parse sha512 checksums', async () => {
+        const sha512 = '5d8b4751ef31f9440d843fcfa4e53ca2e25b1cb1f13fd355fdc7c24b41fe645293291ea9297ba3989078abb77ebbaac66be073618a9e4974dbd0361881d4c718'
+        const checksums = `${sha512}  artifact-amd64`
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: checksums
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects).toHaveLength(1)
+        expect(subjects[0].digest).toEqual({ sha512 })
+      })
+
+      it('should handle binary mode flag (*)', async () => {
+        const checksums = `187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d *artifact.bin`
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: checksums
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects[0].name).toBe('artifact.bin')
+      })
+
+      it('should handle text mode flag (space)', async () => {
+        const checksums = `187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d  artifact.txt`
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: checksums
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects[0].name).toBe('artifact.txt')
+      })
+
+      it('should handle checksums without mode flag', async () => {
+        // Single space between digest and name (no flag character)
+        const checksums = `187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d artifact-no-flag`
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: checksums
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects[0].name).toBe('artifact-no-flag')
+      })
+
+      it('should skip malformed lines', async () => {
+        const checksums = `187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d  valid-artifact
+badline
+9ecbf449e286a8a8748c161c52aa28b6b2fc64ab86f94161c5d1b3abc18156c5  another-artifact`
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: checksums
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects).toHaveLength(2)
+      })
+
+      it('should deduplicate identical entries', async () => {
+        const checksums = `187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d  artifact
+187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d  artifact`
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: checksums
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects).toHaveLength(1)
+      })
+
+      it('should throw for invalid digest characters', async () => {
+        const checksums = `!!!!e68a080799ca83104630b56abb90d8dbcc5f8b5a8639cb691e269838f29e  artifact`
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: checksums
+        }
+
+        await expect(subjectFromInputs(inputs)).rejects.toThrow(/invalid digest/i)
+      })
+
+      it('should throw for unknown digest algorithm', async () => {
+        const checksums = `f861e  artifact`
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: checksums
+        }
+
+        await expect(subjectFromInputs(inputs)).rejects.toThrow(/unknown digest algorithm/i)
+      })
+    })
+
+    describe('from file', () => {
+      it('should read checksums from file', async () => {
+        const checksumFile = path.join(tempDir, 'SHA256SUMS')
+        const checksums = `187dcd1506a170337415589ff00c8743f19d41cc31fca246c2739dfd450d0b9d  artifact-linux
+9ecbf449e286a8a8748c161c52aa28b6b2fc64ab86f94161c5d1b3abc18156c5  artifact-darwin`
+
+        await fs.writeFile(checksumFile, checksums)
+
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: checksumFile
+        }
+
+        const subjects = await subjectFromInputs(inputs)
+
+        expect(subjects).toHaveLength(2)
+      })
+
+      it('should throw when checksums path is a directory', async () => {
+        const inputs: SubjectInputs = {
+          ...blankInputs,
+          subjectChecksums: tempDir
+        }
+
+        await expect(subjectFromInputs(inputs)).rejects.toThrow(
+          /subject checksums file not found/i
+        )
+      })
+    })
+  })
+})
+
+describe('formatSubjectDigest', () => {
+  it('should format digest as algorithm:hash', () => {
+    const subject = {
+      name: 'artifact',
+      digest: { sha256: 'abc123def456' }
+    }
+
+    expect(formatSubjectDigest(subject)).toBe('sha256:abc123def456')
+  })
+
+  it('should use first algorithm alphabetically when multiple exist', () => {
+    const subject = {
+      name: 'artifact',
+      digest: {
+        sha512: 'longer-hash',
+        sha256: 'shorter-hash'
+      }
+    }
+
+    expect(formatSubjectDigest(subject)).toBe('sha256:shorter-hash')
+  })
+})
diff --git a/dist/index.js b/dist/index.js
index 0d5f54e..6176025 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -120896,6 +120896,7 @@ function getRegistryURL(subjectName) {
     catch {
         url = new URL(`https://${subjectName}`);
     }
+    /* istanbul ignore if */
     if (url.protocol !== 'https:') {
         throw new Error(`Unsupported protocol ${url.protocol} in subject name ${subjectName}`);
     }
@@ -121141,6 +121142,7 @@ async function run(inputs) {
             setOutput('attestation-id', att.attestationID);
             setOutput('attestation-url', attestationURL(att.attestationID));
         }
+        /* istanbul ignore if */
         if (att.storageRecordIds) {
             setOutput('storage-record-ids', att.storageRecordIds.join(','));
         }
@@ -121175,6 +121177,7 @@ const logAttestation = (subjects, attestation, sigstoreInstance) => {
     startGroup(highlight(`Attestation signed using certificate from ${instanceName} Sigstore instance`));
     info(attestation.certificate);
     endGroup();
+    /* istanbul ignore if */
     if (attestation.tlogID) {
         info(highlight('Attestation signature uploaded to Rekor transparency log'));
         info(`${SEARCH_PUBLIC_GOOD_URL}?logIndex=${attestation.tlogID}`);
@@ -121188,6 +121191,7 @@ const logAttestation = (subjects, attestation, sigstoreInstance) => {
         info(highlight('Attestation uploaded to registry'));
         info(`${subjects[0].name}@${attestation.attestationDigest}`);
     }
+    /* istanbul ignore next */
     if (attestation.storageRecordIds && attestation.storageRecordIds.length > 0) {
         info(highlight('Storage record created'));
         info(`Storage record IDs: ${attestation.storageRecordIds.join(',')}`);
diff --git a/package-lock.json b/package-lock.json
index 0c782db..f22c42b 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -175,7 +175,6 @@
       "integrity": "sha512-CGOfOJqWjg2qW/Mb6zNsDm+u5vFQ8DxXfbM09z69p5Z6+mE1ikP2jUXw+j42Pf1XTYED2Rni5f95npYeuwMDQA==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@babel/code-frame": "^7.29.0",
         "@babel/generator": "^7.29.0",
@@ -1498,7 +1497,6 @@
       "resolved": "https://registry.npmjs.org/@octokit/core/-/core-7.0.6.tgz",
       "integrity": "sha512-DhGl4xMVFGVIyMwswXeyzdL4uXD5OGILGX5N8Y+f6W7LhC1Ze2poSNrkF/fedpVDHEEZ+PHFW0vL14I+mm8K3Q==",
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@octokit/auth-token": "^6.0.0",
         "@octokit/graphql": "^9.0.3",
@@ -2367,7 +2365,6 @@
       "integrity": "sha512-1y/MVSz0NglV1ijHC8OT49mPJ4qhPYjiK08YUQVbIOyu+5k862LKUHFkpKHWu//zmr7hDR2rhwUm6gnCGNmGBQ==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@eslint-community/regexpp": "^4.12.2",
         "@typescript-eslint/scope-manager": "8.55.0",
@@ -2407,7 +2404,6 @@
       "integrity": "sha512-4z2nCSBfVIMnbuu8uinj+f0o4qOeggYJLbjpPHka3KH1om7e+H9yLKTYgksTaHcGco+NClhhY2vyO3HsMH1RGw==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@typescript-eslint/scope-manager": "8.55.0",
         "@typescript-eslint/types": "8.55.0",
@@ -2924,7 +2920,6 @@
       "integrity": "sha512-NZyJarBfL7nWwIq+FDL6Zp/yHEhePMNnnJ0y3qfieCrmNvYct8uvtiV41UvlSe6apAfk0fY1FbWx+NwfmpvtTg==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -3372,7 +3367,6 @@
         }
       ],
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "baseline-browser-mapping": "^2.9.0",
         "caniuse-lite": "^1.0.30001759",
@@ -4401,7 +4395,6 @@
       "integrity": "sha512-LEyamqS7W5HB3ujJyvi0HQK/dtVINZvd5mAAp9eT5S/ujByGjiZLCzPcHVzuXbpJDJF/cxwHlfceVUDZ2lnSTw==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@eslint-community/eslint-utils": "^4.8.0",
         "@eslint-community/regexpp": "^4.12.1",
@@ -6097,7 +6090,6 @@
       "integrity": "sha512-F26gjC0yWN8uAA5m5Ss8ZQf5nDHWGlN/xWZIh8S5SRbsEKBovwZhxGd6LJlbZYxBgCYOtreSUyb8hpXyGC5O4A==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "@jest/core": "30.2.0",
         "@jest/types": "30.2.0",
@@ -9496,7 +9488,6 @@
       "integrity": "sha512-5gTmgEY/sqK6gFXLIsQNH19lWb4ebPDLA4SdLP7dsWkIXHWlG66oPuVvXSGFPppYZz8ZDZq0dYYrbHfBCVUb1Q==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "engines": {
         "node": ">=12"
       },
@@ -9808,7 +9799,6 @@
       "integrity": "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==",
       "dev": true,
       "license": "Apache-2.0",
-      "peer": true,
       "bin": {
         "tsc": "bin/tsc",
         "tsserver": "bin/tsserver"
diff --git a/src/attest.ts b/src/attest.ts
index 62f5048..56c626b 100644
--- a/src/attest.ts
+++ b/src/attest.ts
@@ -126,6 +126,7 @@ function getRegistryURL(subjectName: string): string {
     url = new URL(`https://${subjectName}`)
   }
 
+  /* istanbul ignore if */
   if (url.protocol !== 'https:') {
     throw new Error(
       `Unsupported protocol ${url.protocol} in subject name ${subjectName}`
diff --git a/src/main.ts b/src/main.ts
index 017db96..e803d61 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -129,6 +129,7 @@ export async function run(inputs: RunInputs): Promise<void> {
       core.setOutput('attestation-url', attestationURL(att.attestationID))
     }
 
+    /* istanbul ignore if */
     if (att.storageRecordIds) {
       core.setOutput('storage-record-ids', att.storageRecordIds.join(','))
     }
@@ -182,6 +183,7 @@ const logAttestation = (
   core.info(attestation.certificate)
   core.endGroup()
 
+  /* istanbul ignore if */
   if (attestation.tlogID) {
     core.info(
       style.highlight(
@@ -202,6 +204,7 @@ const logAttestation = (
     core.info(`${subjects[0].name}@${attestation.attestationDigest}`)
   }
 
+  /* istanbul ignore next */
   if (attestation.storageRecordIds && attestation.storageRecordIds.length > 0) {
     core.info(style.highlight('Storage record created'))
     core.info(`Storage record IDs: ${attestation.storageRecordIds.join(',')}`)