Add unit tests

__tests__/commentManager.test.ts

@@ -0,0 +1,76 @@
+import { previousCommentFor, generateComment } from '../src/commentManager'
+import type { DurationReport } from '../src/types'
+
+describe('previousCommentFor', () => {
+  const validComment = {
+    user: { login: 'github-actions[bot]', type: 'Bot' },
+    body: '🕒 Workflow "Test Workflow" took 60s which is a decrease with 10s (14.29%) compared to latest run on master/main.'
+  }
+
+  it('returns true for a matching GitHub Actions bot comment', () => {
+    const matcher = previousCommentFor('Test Workflow')
+    expect(matcher(validComment)).toBe(true)
+  })
+
+  it('returns false if login is incorrect', () => {
+    const matcher = previousCommentFor('Test Workflow')
+    const comment = {
+      ...validComment,
+      user: { login: 'someone-else', type: 'Bot' }
+    }
+    expect(matcher(comment)).toBe(false)
+  })
+
+  it('returns false if type is not Bot', () => {
+    const matcher = previousCommentFor('Test Workflow')
+    const comment = {
+      ...validComment,
+      user: { login: 'github-actions[bot]', type: 'User' }
+    }
+    expect(matcher(comment)).toBe(false)
+  })
+
+  it('returns false if body does not start with workflow prefix', () => {
+    const matcher = previousCommentFor('Another Workflow')
+    expect(matcher(validComment)).toBe(false)
+  })
+
+  it('returns false if user is null', () => {
+    const matcher = previousCommentFor('Test Workflow')
+    const comment = { ...validComment, user: null }
+    expect(matcher(comment)).toBe(false)
+  })
+})
+
+describe('generateComment', () => {
+  it('returns fallback message when durationReport is undefined', () => {
+    const result = generateComment('My Workflow', undefined)
+    expect(result).toBe(
+      '🕒 Workflow "My Workflow" has no historical runs on master/main branch. Can\'t compare.'
+    )
+  })
+
+  it('generates correct comment for increase', () => {
+    const report: DurationReport = {
+      durationInSeconds: 90,
+      diffInSeconds: 30,
+      diffInPercentage: -50
+    }
+    const result = generateComment('My Workflow', report)
+    expect(result).toBe(
+      '🕒 Workflow "My Workflow" took 90s which is an increase with 30s (50.00%) compared to latest run on master/main.'
+    )
+  })
+
+  it('generates correct comment for decrease', () => {
+    const report: DurationReport = {
+      durationInSeconds: 60,
+      diffInSeconds: -20,
+      diffInPercentage: 25
+    }
+    const result = generateComment('Deploy', report)
+    expect(result).toBe(
+      '🕒 Workflow "Deploy" took 60s which is a decrease with 20s (25.00%) compared to latest run on master/main.'
+    )
+  })
+})

__tests__/durationCalculator.test.ts

@@ -0,0 +1,65 @@
+import { jest } from '@jest/globals'
+import { calculateDuration } from '../src/durationCalculator'
+
+const fixedNow = new Date('2025-01-01T12:00:00Z').getTime()
+
+beforeEach(() => {
+  jest.useFakeTimers().setSystemTime(fixedNow)
+})
+
+afterEach(() => {
+  jest.useRealTimers()
+})
+
+describe('durationAnalyzer', () => {
+  it('returns undefined if no last run is provided', () => {
+    const result = calculateDuration({
+      run_started_at: '2025-01-01T11:50:00Z',
+      updated_at: '2025-01-01T12:00:00Z'
+    })
+    expect(result).toBeUndefined()
+  })
+
+  it('throws error if current.run_started_at is missing', () => {
+    expect(() =>
+      calculateDuration(
+        { updated_at: '2025-01-01T12:00:00Z' },
+        {
+          run_started_at: '2025-01-01T11:00:00Z',
+          updated_at: '2025-01-01T11:10:00Z'
+        }
+      )
+    ).toThrow('Missing run_started_at')
+  })
+
+  it('throws error if last.run_started_at is missing', () => {
+    expect(() =>
+      calculateDuration(
+        {
+          run_started_at: '2025-01-01T11:50:00Z',
+          updated_at: '2025-01-01T12:00:00Z'
+        },
+        { updated_at: '2025-01-01T11:10:00Z' }
+      )
+    ).toThrow('Missing run_started_at')
+  })
+
+  it('calculates duration and difference correctly', () => {
+    const result = calculateDuration(
+      {
+        run_started_at: '2025-01-01T11:59:00Z',
+        updated_at: '2025-01-01T12:00:00Z'
+      },
+      {
+        run_started_at: '2025-01-01T11:00:00Z',
+        updated_at: '2025-01-01T11:10:00Z'
+      }
+    )
+
+    expect(result).toEqual({
+      durationInSeconds: 60,
+      diffInSeconds: -(9 * 60),
+      diffInPercentage: 90
+    })
+  })
+})

__tests__/main.test.ts

@@ -1,5 +1,165 @@
-describe('main.ts', () => {
-  it('is truthy', () => {
-    expect(true).toBeTruthy()
+import { jest } from '@jest/globals'
+import type { GhActionsContext } from '../src/types'
+
+const getCurrentWorkflowRun = jest.fn()
+const listWorkflowRuns = jest.fn()
+const listComments = jest.fn()
+const createComment = jest.fn()
+const updateComment = jest.fn()
+
+jest.unstable_mockModule('../src/githubClient.js', () => ({
+  default: class {
+    getCurrentWorkflowRun = getCurrentWorkflowRun
+    listWorkflowRuns = listWorkflowRuns
+    listComments = listComments
+    createComment = createComment
+    updateComment = updateComment
+  }
+}))
+
+const DEFAULT_CONTEXT: GhActionsContext = {
+  eventName: '',
+  workflow: '',
+  issue: {
+    number: 0
+  },
+  repo: {
+    owner: '',
+    repo: ''
+  },
+  runId: 0
+}
+
+const DEFAULT_WORKFLOW_RUN = {
+  workflow_id: 0,
+  head_branch: '',
+  status: '',
+  conclusion: '',
+  run_started_at: '2025-04-29T14:05:00Z',
+  updated_at: '2025-04-29T14:07:00Z'
+}
+
+const fixedNow = new Date('2025-04-29T14:00:00Z')
+
+describe('main', () => {
+  let run: typeof import('../src/main.js').run
+
+  beforeEach(async () => {
+    jest.useFakeTimers().setSystemTime(fixedNow.getTime())
+    const mainModule = await import('../src/main.js')
+    run = mainModule.run
+
+    listComments.mockReturnValue(
+      Promise.resolve({
+        data: []
+      })
+    )
+    listWorkflowRuns.mockReturnValue(
+      Promise.resolve({
+        data: {
+          workflow_runs: []
+        }
+      })
+    )
+    getCurrentWorkflowRun.mockReturnValue(
+      Promise.resolve({
+        data: {
+          ...DEFAULT_WORKFLOW_RUN
+        }
+      })
+    )
+  })
+
+  afterEach(() => {
+    jest.useRealTimers()
+  })
+
+  it('does nothing for non-pull_request events', async () => {
+    await run(
+      { ...DEFAULT_CONTEXT, eventName: 'not-pull_request' },
+      'fake-token'
+    )
+    expect(createComment).not.toHaveBeenCalled()
+    expect(updateComment).not.toHaveBeenCalled()
+  })
+
+  it('creates comment if no previous one is found', async () => {
+    await run(
+      {
+        ...DEFAULT_CONTEXT,
+        eventName: 'pull_request',
+        workflow: 'My workflow'
+      },
+      'fake-token'
+    )
+
+    expect(createComment).toHaveBeenCalledWith(
+      '🕒 Workflow "My workflow" has no historical runs on master/main branch. Can\'t compare.'
+    )
+  })
+
+  it('updates comment if previous one is found', async () => {
+    listComments.mockReturnValueOnce(
+      Promise.resolve({
+        data: [
+          {
+            id: 42,
+            user: {
+              login: 'github-actions[bot]',
+              type: 'Bot'
+            },
+            body: '🕒 Workflow "Another workflow" took...'
+          }
+        ]
+      })
+    )
+    await run(
+      {
+        ...DEFAULT_CONTEXT,
+        eventName: 'pull_request',
+        workflow: 'Another workflow'
+      },
+      'fake-token'
+    )
+
+    expect(updateComment).toHaveBeenCalledWith(
+      42,
+      '🕒 Workflow "Another workflow" has no historical runs on master/main branch. Can\'t compare.'
+    )
+  })
+
+  it('includes duration information if previous workflow run is found', async () => {
+    getCurrentWorkflowRun.mockReturnValueOnce({
+      data: {
+        run_started_at: '2025-04-29T13:57:00Z',
+        workflow_id: 42
+      }
+    })
+    listWorkflowRuns.mockReturnValueOnce({
+      data: {
+        workflow_runs: [
+          {
+            ...DEFAULT_WORKFLOW_RUN,
+            run_started_at: '2025-04-28T13:55:00Z',
+            updated_at: '2025-04-28T13:56:00Z',
+            head_branch: 'main',
+            status: 'completed',
+            conclusion: 'success'
+          }
+        ]
+      }
+    })
+    await run(
+      {
+        ...DEFAULT_CONTEXT,
+        eventName: 'pull_request',
+        workflow: 'Some workflow'
+      },
+      'fake-token'
+    )
+
+    expect(createComment).toHaveBeenCalledWith(
+      '🕒 Workflow "Some workflow" took 180s which is an increase with 120s (200.00%) compared to latest run on master/main.'
+    )
   })
 })