# How to Run Tests in Munder Difflin Using Node's Built-in Test Runner

> Learn to run tests in Munder Difflin using Node's built-in test runner. Execute the full suite with `node --test test/**/*.test.cjs` or use `npm run test:focused`.

- Repository: [Chaitanya Giri/munder-difflin](https://github.com/chaitanyagiri/munder-difflin)
- Tags: how-to-guide
- Published: 2026-08-20

---

**Run the full test suite in munder-difflin with `node --test test/**/*.test.cjs` or use the `npm run test:focused` convenience script.**

The munder-difflin repository uses Node.js v18+'s native test runner rather than a third-party framework like Jest or Mocha. This approach eliminates extra dependencies and leverages the `--test` flag introduced in Node 18. The test files follow the `*.test.cjs` naming convention and reside in the `test/` directory.

## Prerequisites

Before running tests, ensure you have:

- **Node.js v18 or higher** — the native test runner requires this version
- **npm** — package manager for installing dependencies

The repository also depends on native modules like `node-pty`, which rebuild automatically during installation via the `postinstall` script defined in [`package.json`](https://github.com/chaitanyagiri/munder-difflin/blob/main/package.json).

## Step 1: Clone and Install

Start by cloning the repository and installing dependencies:

```bash
git clone https://github.com/chaitanyagiri/munder-difflin.git
cd munder-difflin
npm install

```

The `npm install` command triggers the `postinstall` script in [`package.json`](https://github.com/chaitanyagiri/munder-difflin/blob/main/package.json) (lines 14–19), which rebuilds native addons including `node-pty`. This step is essential — skipping it will cause test failures related to terminal emulation.

## Step 2: Run the Full Test Suite

Munder difflin offers two equivalent ways to execute all tests:

**Option A: Direct Node command (recommended)**

```bash
node --test test/**/*.test.cjs

```

**Option B: Package.json script**

```bash
npm run test:focused

```

The `test:focused` script in [`package.json`](https://github.com/chaitanyagiri/munder-difflin/blob/main/package.json) (lines 22–23) wraps the same `node --test` invocation with an explicit file list. Both methods produce identical TAP-formatted output showing pass (`✔`) or fail (`✖`) status for each test.

## Step 3: Run Specific Test Files

For faster feedback during development, target individual test files or patterns:

```bash

# Single test file

node --test test/hero-payload.test.cjs

# Pattern-based filtering

node --test test/**/skills*.test.cjs
node --test test/*/provider-*.test.cjs

```

Node's test runner accepts any glob pattern supported by your shell, making it easy to isolate problematic tests without running the entire suite.

## Understanding Test Output

The native test runner outputs TAP (Test Anything Protocol) format by default:

- Passing tests display with `✔` and completion time
- Failing tests show `✖` with stack traces
- Exit code `0` indicates success; non-zero indicates failures

Check the exit code explicitly on Unix systems:

```bash
node --test test/**/*.test.cjs
echo $?   # 0 = all passed, non-zero = failures detected

```

## Key Configuration Files

Understanding these files helps when customizing test execution:

| File | Purpose |
|------|---------|
| [`package.json`](https://github.com/chaitanyagiri/munder-difflin/blob/main/package.json) | Defines `scripts.postinstall` for native rebuilds and `scripts.test:focused` for test execution |
| `test/` | Contains all `*.test.cjs` test files organized by feature |
| [`README.md`](https://github.com/chaitanyagiri/munder-difflin/blob/main/README.md) (lines 85–90) | Documents clone and install procedures |

The `postinstall` script is particularly important — it ensures `node-pty` and other native dependencies are compiled for your specific platform before tests attempt to use them.

## Complete Workflow Example

From a fresh environment to verified tests:

```bash

# Clone and setup

git clone https://github.com/chaitanyagiri/munder-difflin.git
cd munder-difflin
npm install

# Run all tests

npm run test:focused

# Or run directly with Node

node --test test/**/*.test.cjs

```

## Summary

- **Munder difflin uses Node v18+'s native `node --test`** — no Jest, Mocha, or other test runner required
- **Install with `npm install`** to trigger native module rebuilds via `postinstall`
- **Execute tests with `node --test test/**/*.test.cjs`** or the `npm run test:focused` wrapper
- **Filter tests using shell globs** for faster development cycles
- **All test files use the `.test.cjs` extension** and live in the `test/` directory

## Frequently Asked Questions

### What Node version is required to run tests in munder-difflin?

Node.js v18 or higher is required. The repository relies on the native `--test` flag introduced in Node 18, which provides built-in test running without external dependencies.

### Why does `npm test` not work in this repository?

The [`package.json`](https://github.com/chaitanyagiri/munder-difflin/blob/main/package.json) does not define a standard `test` script. Instead, it exposes `test:focused` as the primary test command. You can run `npm run test:focused` or invoke `node --test` directly with your desired file pattern.

### What happens if tests fail with errors about `node-pty`?

This indicates the `postinstall` script did not complete successfully during `npm install`. Run `npm install` again and check for compilation errors in the output. The `node-pty` native module must be rebuilt for your platform before terminal-related tests can execute.

### Can I watch tests and re-run on file changes?

Node's native test runner does not include a watch mode. For automatic re-running, use a file watcher like `nodemon` or `chokidar-cli` wrapped around the test command, or rely on your editor's test runner integration.