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268 changes: 268 additions & 0 deletions recipes/mocha-to-node-test-runner/README.md
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# Mocha to Node.js Test Runner

This codemod converts Mocha v8 tests to Node.js test runner (v22, v24).

## Features

- Automatically adds `node:test` imports/requires
- Converts global `describe`, `it`, and hooks to imported versions
- Transforms `done` callbacks to `(t, done)` signature
- Converts `this.skip()` to `t.skip()`
- Converts `this.timeout()` to `{ timeout: N }` options
- Preserves function styles (doesn't convert between `function()` and arrow functions)
- Supports both CommonJS and ESM

## Important Points

- Does **not** touch imports except `mocha` imports and `node:test` imports
- Does **not** convert callback style from `function()` to arrow functions `() => {}` or vice versa
- Supports both CJS and ESM

## Examples

### Example 1: Basic Test Case

**Before:**

```js
const assert = require('assert');
describe('Array', function() {
describe('#indexOf()', function() {
it('should return -1 when the value is not present', function() {
const arr = [1, 2, 3];
assert.strictEqual(arr.indexOf(4), -1);
});
});
});
```

**After:**

```js
const assert = require('assert');
const { describe, it } = require('node:test');
describe('Array', function() {
describe('#indexOf()', function() {
it('should return -1 when the value is not present', function() {
const arr = [1, 2, 3];
assert.strictEqual(arr.indexOf(4), -1);
});
});
});
```

### Example 2: Async Test Case

**Before:**

```js
const assert = require('assert');
describe('Async Test', function() {
it('should complete after a delay', async function(done) {
const result = await new Promise(resolve => setTimeout(() => resolve(42), 100));
assert.strictEqual(result, 42);
});
});
```

**After:**

```js
const assert = require('assert');
const { describe, it } = require('node:test');
describe('Async Test', function() {
it('should complete after a delay', async function() {
const result = await new Promise(resolve => setTimeout(() => resolve(42), 100));
assert.strictEqual(result, 42);
});
});
```

### Example 3: Hooks

**Before:**

```js
const assert = require('assert');
const fs = require('fs');
describe('File System', function() {
before(function() {
fs.writeFileSync('test.txt', 'Hello, World!');
});

after(function() {
fs.unlinkSync('test.txt');
});

it('should read the file', function() {
const content = fs.readFileSync('test.txt', 'utf8');
assert.strictEqual(content, 'Hello, World!');
});
});
```

**After:**

```js
const assert = require('assert');
const fs = require('fs');
const { describe, before, after, it } = require('node:test');
describe('File System', function() {
before(function() {
fs.writeFileSync('test.txt', 'Hello, World!');
});

after(function() {
fs.unlinkSync('test.txt');
});

it('should read the file', function() {
const content = fs.readFileSync('test.txt', 'utf8');
assert.strictEqual(content, 'Hello, World!');
});
});
```

### Example 4: `done` Callback

**Before:**

```js
const assert = require('assert');
describe('Callback Test', function() {
it('should call done when complete', function(done) {
setTimeout(() => {
assert.strictEqual(1 + 1, 2);
done();
}, 100);
});
});
```

**After:**

```js
const assert = require('assert');
const { describe, it } = require('node:test');
describe('Callback Test', function() {
it('should call done when complete', (t, done) => {
setTimeout(() => {
assert.strictEqual(1 + 1, 2);
done();
}, 100);
});
});
```

### Example 5: Skipped Tests

**Before:**

```js
const assert = require('assert');
describe('Skipped Test', function() {
it.skip('should not run this test', function() {
assert.strictEqual(1 + 1, 3);
});
it('should also be skipped', function() {
this.skip();
assert.strictEqual(1 + 1, 3);
});
});
```

**After:**

```js
const assert = require('assert');
const { describe, it } = require('node:test');
describe('Skipped Test', function() {
it.skip('should not run this test', function() {
assert.strictEqual(1 + 1, 3);
});
it('should also be skipped', (t) => {
assert.strictEqual(1 + 1, 3);
t.skip();
});
});
```

### Example 6: Dynamic/generated tests

**Before:**

```js
const assert = require('assert');
describe('Dynamic Tests', function() {
const tests = [1, 2, 3];
tests.forEach((test) => {
it(`should handle test ${test}`, function() {
assert.strictEqual(test % 2, 0);
});
});
});
```

**After:**

```js
const assert = require('assert');
const { describe, it } = require('node:test');
describe('Dynamic Tests', function() {
const tests = [1, 2, 3];
tests.forEach((test) => {
it(`should handle test ${test}`, function() {
assert.strictEqual(test % 2, 0);
});
});
});
```

### Example 7: Timeouts handling

This timeout handling works for `describe`, `it` and hooks.

**Before:**

```js
const assert = require('assert');
describe('Timeout Test', function() {
this.timeout(500);

it('should complete within 100ms', function(done) {
this.timeout(100);
setTimeout(done, 500); // This will fail

});

it('should complete within 200ms', function() {
this.timeout(200);
setTimeout(done, 100); // This will pass
});
});
```

**After:**

```js
const assert = require('assert');
const { describe, it } = require('node:test');
describe('Timeout Test', { timeout: 500 }, function() {
it('should complete within 100ms', { timeout: 100 }, (t, done) => {
setTimeout(done, 500); // This will fail
});

it('should complete within 200ms', { timeout: 200 }, (t, done) => {
setTimeout(done, 100); // This will pass
});
});
```

## Caveats

- `node:test` doesn't support the `retry` option that Mocha has, so any tests using that will need to be handled separately.

## References

- [Node Test Runner](https://nodejs.org/api/test.html)
- [Mocha](https://mochajs.org/)
23 changes: 23 additions & 0 deletions recipes/mocha-to-node-test-runner/codemod.yaml
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schema_version: "1.0"
name: "@nodejs/mocha-to-node-test-runner"
version: 1.0.0
description: "Converts Mocha v8 tests to Node.js test runner (v22, v24)"
author: "Elio Capella <[email protected]>"
license: MIT
workflow: workflow.yaml
category: migration

targets:
languages:
- javascript
- typescript

keywords:
- transformation
- migration
- mocha
- testing

registry:
access: public
visibility: public
24 changes: 24 additions & 0 deletions recipes/mocha-to-node-test-runner/package.json
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{
"name": "@nodejs/mocha-to-node-test-runner",
"version": "1.0.0",
"description": "Converts Mocha v8 tests to Node.js test runner (v22, v24)",
"type": "module",
"scripts": {
"test": "npx codemod@next jssg test -l typescript ./src/workflow.ts ./"
},
"repository": {
"type": "git",
"url": "git+https://github.com/nodejs/userland-migrations.git",
"directory": "recipes/mocha-to-node-test-runner",
"bugs": "https://github.com/nodejs/userland-migrations/issues"
},
"author": "Elio Capella",
"license": "MIT",
"homepage": "https://github.com/nodejs/userland-migrations/blob/main/recipes/mocha-to-node-test-runner/README.md",
"devDependencies": {
"@codemod.com/jssg-types": "^1.0.3"
},
"dependencies": {
"@nodejs/codemod-utils": "0.0.0"
}
}
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