Update @actions/core to v3

This updates @actions/core from v2 to v3, which is an ESM-only package.

Changes required for ESM compatibility:
- Add jest.config.mjs with ts-jest ESM preset
- Update test script to use --experimental-vm-modules
- Update test files to use jest.unstable_mockModule() for ESM mocking
- Import jest from @jest/globals instead of using globals
- Use dynamic imports after setting up mocks
- Fix __dirname usage in src/collect.ts using import.meta.url

Fixes #66

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: JKRT

__tests__/collect.test.ts

@@ -4,15 +4,39 @@
 
 import * as fs from 'fs'
 import * as path from 'path'
-import * as artifact from '@actions/artifact'
-import { expect } from '@jest/globals'
-import { copyHtmlFilesSync, uploadArtifacts } from '../src/collect'
+import {
+  expect,
+  jest,
+  describe,
+  beforeEach,
+  afterEach,
+  it
+} from '@jest/globals'
 
 const tempTestDir = path.join('__tests__', 'tmp-collect')
 
 // Mock @actions/artifact
-jest.mock('@actions/artifact')
-jest.mock('@actions/github')
+const uploadArtifactMock = jest
+  .fn<() => Promise<{ size: number; id: number }>>()
+  .mockResolvedValue({ size: 0, id: 0 })
+
+const DefaultArtifactClientMock = jest.fn().mockImplementation(() => ({
+  uploadArtifact: uploadArtifactMock
+}))
+
+jest.unstable_mockModule('@actions/artifact', () => ({
+  DefaultArtifactClient: DefaultArtifactClientMock
+}))
+
+jest.unstable_mockModule('@actions/github', () => ({
+  context: {
+    repo: { owner: 'test', repo: 'test' },
+    runId: 123
+  }
+}))
+
+// Dynamic imports after mocking
+const { copyHtmlFilesSync, uploadArtifacts } = await import('../src/collect')
 
 function mockFileStructure(
   libraryName: string,
@@ -107,13 +131,6 @@ describe('collect.ts', () => {
     const targetDir = path.join(tempTestDir, 'html')
     mockFileStructure(libraryName, libraryVersion, modelPrefix, omLibTestingDir)
 
-    const DefaultArtifactClientMock = jest
-      .spyOn(artifact, 'DefaultArtifactClient')
-      .mockImplementation()
-    const uploadArtifactMock = jest
-      .spyOn(artifact.DefaultArtifactClient.prototype, 'uploadArtifact')
-      .mockImplementation()
-
     copyHtmlFilesSync(
       libraryName,
       libraryVersion,

__tests__/index.test.ts

@@ -2,15 +2,19 @@
  * Unit tests for the action's entrypoint, src/index.ts
  */
 
-import * as main from '../src/main'
+import { expect, jest, describe, it } from '@jest/globals'
 
-// Mock the action's entrypoint
-const runMock = jest.spyOn(main, 'run').mockImplementation()
+// Mock the main module before importing
+const runMock = jest.fn<() => Promise<void>>().mockResolvedValue(undefined)
+
+jest.unstable_mockModule('../src/main', () => ({
+  run: runMock
+}))
 
 describe('index', () => {
   it('calls run when imported', async () => {
-    // eslint-disable-next-line @typescript-eslint/no-require-imports
-    require('../src/index')
+    // Dynamic import after mocking
+    await import('../src/index')
 
     expect(runMock).toHaveBeenCalled()
   })

__tests__/inputs.test.ts

@@ -3,20 +3,32 @@
  */
 
 import * as path from 'path'
-import * as core from '@actions/core'
-import { expect } from '@jest/globals'
-import { ActionInputs, ActionInputsInterface } from '../src/inputs'
+import { expect, jest, describe, beforeEach, it } from '@jest/globals'
 
 const modelicaFile = path.resolve('examples/MyLibrary/package.mo')
 const referenceFilesDir = path.resolve('examples/ReferenceFiles')
 
-// Mock the GitHub Actions core library
-let getInputMock: jest.SpyInstance
+// Mock @actions/core before importing modules that use it
+const getInputMock =
+  jest.fn<(name: string, options?: { required?: boolean }) => string>()
+
+jest.unstable_mockModule('@actions/core', () => ({
+  getInput: getInputMock,
+  debug: jest.fn(),
+  info: jest.fn(),
+  warning: jest.fn(),
+  error: jest.fn(),
+  setFailed: jest.fn(),
+  setOutput: jest.fn()
+}))
+
+// Dynamic import after mocking
+const { ActionInputs } = await import('../src/inputs')
+import type { ActionInputsInterface } from '../src/inputs'
 
 describe('inputs.ts', () => {
   beforeEach(() => {
     jest.clearAllMocks()
-    getInputMock = jest.spyOn(core, 'getInput').mockImplementation()
   })
 
   it('Read inputs', async () => {

__tests__/main.test.ts

@@ -9,33 +9,68 @@
 import * as fs from 'fs'
 import * as os from 'os'
 import * as path from 'path'
-import * as core from '@actions/core'
-import * as main from '../src/main'
-import { getMSYS } from '../src/get-msys'
+import { expect, jest, describe, beforeEach, afterAll, it } from '@jest/globals'
 
 // Some expected string
 const mdCoverageTable = `| Total | Frontend | Backend | SimCode | Templates | Compilation | Simulation | Verification |
 | --- | --- | --- | --- | --- | --- | --- | --- |
 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 1 |`
 
-// Mock the action's main function
-const runMock = jest.spyOn(main, 'run')
 const modelicaFile = path.resolve(
   path.join('examples', 'MyLibrary', 'package.mo')
 )
 const referenceFilesDir = path.resolve(path.join('examples', 'ReferenceFiles'))
 
 // Mock the GitHub Actions core library
-let debugMock: jest.SpyInstance
-let errorMock: jest.SpyInstance
-let infoMock: jest.SpyInstance
-let getInputMock: jest.SpyInstance
-let setFailedMock: jest.SpyInstance
-let setOutputMock: jest.SpyInstance
+const debugMock = jest
+  .fn<(message: string) => void>()
+  .mockImplementation(msg => console.log(`::debug::${msg}`))
+const infoMock = jest
+  .fn<(message: string) => void>()
+  .mockImplementation(msg => console.log(`::info::${msg}`))
+const errorMock = jest
+  .fn<(message: string | Error) => void>()
+  .mockImplementation(msg => console.log(`::error::${msg}`))
+const getInputMock =
+  jest.fn<(name: string, options?: { required?: boolean }) => string>()
+const setFailedMock = jest.fn<(message: string | Error) => void>()
+const setOutputMock = jest.fn<(name: string, value: unknown) => void>()
+
+jest.unstable_mockModule('@actions/core', () => ({
+  debug: debugMock,
+  info: infoMock,
+  warning: jest.fn(),
+  error: errorMock,
+  getInput: getInputMock,
+  setFailed: setFailedMock,
+  setOutput: setOutputMock,
+  summary: {
+    addRaw: jest.fn().mockReturnThis(),
+    write: jest.fn<() => Promise<void>>().mockResolvedValue(undefined)
+  }
+}))
 
 // Mock @actions/artifact and @actions/github
-jest.mock('@actions/artifact')
-jest.mock('@actions/github')
+const uploadArtifactMock = jest
+  .fn<() => Promise<{ size: number; id: number }>>()
+  .mockResolvedValue({ size: 0, id: 0 })
+
+jest.unstable_mockModule('@actions/artifact', () => ({
+  DefaultArtifactClient: jest.fn().mockImplementation(() => ({
+    uploadArtifact: uploadArtifactMock
+  }))
+}))
+
+jest.unstable_mockModule('@actions/github', () => ({
+  context: {
+    repo: { owner: 'test', repo: 'test' },
+    runId: 123
+  }
+}))
+
+// Dynamic imports after mocking
+const main = await import('../src/main')
+const { getMSYS } = await import('../src/get-msys')
 
 // Set GitHub summary file
 const gitHubStepSummaryFile = path.resolve(
@@ -57,18 +92,9 @@ describe('action', () => {
 
     jest.clearAllMocks()
 
-    debugMock = jest
-      .spyOn(core, 'debug')
-      .mockImplementation(msg => console.log(`::debug::${msg}`))
-    infoMock = jest
-      .spyOn(core, 'info')
-      .mockImplementation(msg => console.log(`::info::${msg}`))
-    errorMock = jest
-      .spyOn(core, 'error')
-      .mockImplementation(msg => console.log(`::error::${msg}`))
-    getInputMock = jest.spyOn(core, 'getInput').mockImplementation()
-    setFailedMock = jest.spyOn(core, 'setFailed').mockImplementation()
-    setOutputMock = jest.spyOn(core, 'setOutput').mockImplementation()
+    debugMock.mockImplementation(msg => console.log(`::debug::${msg}`))
+    infoMock.mockImplementation(msg => console.log(`::info::${msg}`))
+    errorMock.mockImplementation(msg => console.log(`::error::${msg}`))
   })
 
   it(
@@ -101,7 +127,6 @@ describe('action', () => {
       })
 
       await main.run()
-      expect(runMock).toHaveReturned()
 
       // Verify that all of the core library functions were called correctly
       expect(debugMock).toHaveBeenNthCalledWith(1, 'Get inputs')