Add a single unit test

.github/workflows/ci.yml

@@ -34,5 +34,9 @@ jobs:
         id: npm-lint
         run: npm run lint
 
+      - name: Test
+        id: npm-test
+        run: npm run test
+
       - name: Workflow timer
         uses: './'

.gitignore

@@ -1,2 +1,3 @@
 node_modules
+coverage
 

__tests__/main.test.ts

@@ -0,0 +1,5 @@
+describe('main.ts', () => {
+  it('is truthy', () => {
+    expect(true).toBeTruthy()
+  })
+})

jest.config.js

@@ -0,0 +1,29 @@
+// See: https://jestjs.io/docs/configuration
+
+/** @type {import('ts-jest').JestConfigWithTsJest} **/
+export default {
+  clearMocks: true,
+  collectCoverage: true,
+  collectCoverageFrom: ['./src/**'],
+  coverageDirectory: './coverage',
+  coveragePathIgnorePatterns: ['/node_modules/', '/dist/'],
+  coverageReporters: ['json-summary', 'text', 'lcov'],
+  extensionsToTreatAsEsm: ['.ts'],
+  moduleFileExtensions: ['ts', 'js'],
+  preset: 'ts-jest',
+  reporters: ['default'],
+  resolver: 'ts-jest-resolver',
+  testEnvironment: 'node',
+  testMatch: ['**/*.test.ts'],
+  testPathIgnorePatterns: ['/dist/', '/node_modules/'],
+  transform: {
+    '^.+\\.ts$': [
+      'ts-jest',
+      {
+        tsconfig: 'tsconfig.eslint.json',
+        useESM: true
+      }
+    ]
+  },
+  verbose: true
+}

package.json

@@ -17,8 +17,9 @@
     "lint": "npx eslint .",
     "package": "npx rollup --config rollup.config.ts --configPlugin @rollup/plugin-typescript",
     "package:watch": "npm run package -- --watch",
+    "test": "NODE_OPTIONS=--experimental-vm-modules NODE_NO_WARNINGS=1 npx jest",
     "tsc": "tsc --noEmit",
-    "all": "npm run format:write && npm run lint && npm run tsc && npm run package"
+    "all": "npm run format:write && npm run lint && npm run test && npm run tsc && npm run package"
   },
   "dependencies": {
     "@actions/core": "^1.11.1",
@@ -29,6 +30,7 @@
     "@rollup/plugin-commonjs": "^28.0.3",
     "@rollup/plugin-node-resolve": "^16.0.1",
     "@rollup/plugin-typescript": "^12.1.2",
+    "@types/jest": "^29.5.14",
     "@types/node": "^22.15.2",
     "@typescript-eslint/eslint-plugin": "^8.31.0",
     "@typescript-eslint/parser": "^8.31.0",