Add a quick regression test for the artefact summary

__tests__/main.test.ts

@@ -0,0 +1,153 @@
+import {
+  afterEach,
+  beforeEach,
+  describe,
+  expect,
+  jest,
+  test
+} from '@jest/globals'
+import * as fs from 'fs'
+import * as core from '@actions/core'
+import {DefaultArtifactClient} from '@actions/artifact'
+import type {SpyInstance} from 'jest-mock'
+import {handleLargeSummary} from '../src/main'
+
+jest.mock('ansi-styles', () => ({
+  __esModule: true,
+  default: {
+    color: {
+      red: {open: '', close: ''},
+      yellow: {open: '', close: ''},
+      grey: {open: '', close: ''},
+      green: {open: '', close: ''}
+    },
+    bold: {open: '', close: ''}
+  }
+}))
+jest.mock('../src/dependency-graph', () => ({}))
+jest.mock('@actions/core', () => {
+  const summary = {
+    addRaw: jest.fn().mockReturnThis(),
+    addHeading: jest.fn().mockReturnThis(),
+    addTable: jest.fn().mockReturnThis(),
+    addSeparator: jest.fn().mockReturnThis(),
+    addImage: jest.fn().mockReturnThis(),
+    addList: jest.fn().mockReturnThis(),
+    addBreak: jest.fn().mockReturnThis(),
+    addLink: jest.fn().mockReturnThis(),
+    addDetails: jest.fn().mockReturnThis(),
+    addSection: jest.fn().mockReturnThis(),
+    addCodeBlock: jest.fn().mockReturnThis(),
+    addFields: jest.fn().mockReturnThis(),
+    addEol: jest.fn().mockReturnThis(),
+    write: jest.fn(async () => undefined),
+    emptyBuffer: jest.fn(),
+    stringify: jest.fn(() => '')
+  }
+  return {
+    __esModule: true,
+    getInput: jest.fn((name: string) =>
+      name === 'repo-token' ? 'gh_test_token' : ''
+    ),
+    setOutput: jest.fn(),
+    setFailed: jest.fn(),
+    warning: jest.fn(),
+    info: jest.fn(),
+    debug: jest.fn(),
+    startGroup: jest.fn(),
+    endGroup: jest.fn(),
+    group: jest.fn(async (_name: string, fn: () => Promise<unknown>) => fn()),
+    summary
+  }
+})
+jest.mock('@actions/artifact', () => ({
+  DefaultArtifactClient: jest.fn()
+}))
+
+const ORIGINAL_ENV = {...process.env}
+
+type ArtifactClientInstance = {
+  uploadArtifact: jest.Mock
+}
+
+const DefaultArtifactClientMock = DefaultArtifactClient as unknown as jest.Mock
+
+const createArtifactClient = (): ArtifactClientInstance => ({
+  uploadArtifact: jest.fn(async () => undefined)
+})
+
+describe('handleLargeSummary', () => {
+  let writeFileSpy: SpyInstance<typeof fs.promises.writeFile>
+
+  beforeEach(() => {
+    process.env = {...ORIGINAL_ENV}
+    writeFileSpy = jest
+      .spyOn(fs.promises, 'writeFile')
+      .mockImplementation(async () => undefined)
+    DefaultArtifactClientMock.mockClear()
+    DefaultArtifactClientMock.mockImplementation(() => createArtifactClient())
+  })
+
+  afterEach(() => {
+    writeFileSpy.mockRestore()
+    jest.clearAllMocks()
+    process.env = {...ORIGINAL_ENV}
+  })
+
+  test('returns original summary when under size threshold', async () => {
+    const summaryContent = 'short summary'
+
+    const result = await handleLargeSummary(summaryContent)
+
+    expect(result).toBe(summaryContent)
+    expect(writeFileSpy).not.toHaveBeenCalled()
+    expect(DefaultArtifactClientMock).not.toHaveBeenCalled()
+  })
+
+  test('uploads artifact and returns minimal summary when summary is too large', async () => {
+    process.env.GITHUB_SERVER_URL = 'https://github.com'
+    process.env.GITHUB_REPOSITORY = 'owner/repo'
+    process.env.GITHUB_RUN_ID = '12345'
+
+    const largeSummary = 'a'.repeat(1024 * 1024 + 1)
+
+    const result = await handleLargeSummary(largeSummary)
+
+    expect(writeFileSpy).toHaveBeenCalledTimes(1)
+    expect(writeFileSpy).toHaveBeenCalledWith('summary.md', largeSummary)
+    expect(DefaultArtifactClientMock).toHaveBeenCalledTimes(1)
+
+    const artifactInstance = DefaultArtifactClientMock.mock.results[0]
+      ?.value as ArtifactClientInstance
+
+    expect(artifactInstance.uploadArtifact).toHaveBeenCalledWith(
+      'dependency-review-summary',
+      ['summary.md'],
+      '.',
+      {retentionDays: 1}
+    )
+
+    expect(result).toContain('# Dependency Review Summary')
+    expect(result).toContain('dependency-review-summary')
+    expect(result).toContain('actions/runs/12345')
+  })
+
+  test('returns original summary and logs a warning when artifact handling fails', async () => {
+    const warningMock = core.warning as jest.Mock
+    warningMock.mockClear()
+    const largeSummary = 'b'.repeat(1024 * 1024 + 1)
+
+    DefaultArtifactClientMock.mockImplementation(() => ({
+      uploadArtifact: jest.fn(async () => {
+        throw new Error('upload failed')
+      })
+    }))
+
+    const result = await handleLargeSummary(largeSummary)
+
+    expect(result).toBe(largeSummary)
+    expect(warningMock).toHaveBeenCalledWith(
+      expect.stringContaining('Failed to handle large summary')
+    )
+  })
+})