Easy unit testing in node.js, loosely based on the QUnit API
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If you're looking for a full-featured and descriptive specification framework you might want to checkout a project like the excellent jspec. If, like me, you just want to dive into writing some code and don't want to learn an extensive framework before writing tests, then nodeunit could be for you.

nodeunit offers easy unit testing based on a simplified version of the QUnit API. However, unlike QUnit, it assumes all your tests are asynchronous, and plays nicely with the existing module system. Because of these assumptions, the already minimal API offered by QUnit can be further reduced.

nodeunit is available as an npm package:

npm install nodeunit



Here is an example unit test module:

exports.testSomething = function(test){
    test.ok(true, "this assertion should pass");

exports.testSomethingElse = function(test){
    test.ok(false, "this assertion should fail");

When run using the included testrunner, this will output the following:

API Documentation

  • expect(amount) - Specify how many assertions are expected to run within a test.
  • ok(state, message) - A boolean assertion, equivalent to assert.ok
  • equals(actual, expected, message) - A comparison assertion, equivalent to assert.equal
  • same(actual, expected, message) - A deep recursive comparison, equivalent to assert.deepEquals
  • done() - Finish this test function, and move on to the next. ALL tests should call this!

These 5 functions are all you need to know!

nodeunit aims to be simple and easy to learn. This is achieved through using existing structures (such as node.js modules) to maximum effect, and reducing the API where possible, to make it easier to digest.

Tests are simply exported from a module, but they are still run in the order they are defined. The module() call from QUnit can be omitted, since it is inside a module file, and we can refer to it by filename.

Asynchronous Testing

When testing asynchronous code, there are a number of sharp edges to watch out for. Thankfully, nodeunit is designed to help you avoid as many of these pitfalls as possible. For the most part, testing asynchronous code in nodeunit just works.

Tests run in series

While running tests in parallel seems like a good idea for speeding up your test suite, in practice I've found it means writing much more complicated tests. Because of node's module cache, running tests in parallel means mocking and stubbing is pretty much impossible. One of the nicest things about testing in javascript is the ease of doing stubs:

var _readFile = fs.readFile;
fs.readFile = function(path, callback){
    // its a stub!
// test function that uses fs.readFile

// we're done
fs.readFile = _readFile;

You cannot do this when running tests in parallel. In order to keep testing as simple as possible, nodeunit avoids it. Thankfully, most unit-test suites run fast anyway.

Explicit ending of tests

When testing async code its important that tests end at the correct point, not just after a given number of assertions. Otherwise your tests can run short, ending before all assertions have completed. Its important to detect too many assertions as well as too few. Combining explicit ending of tests with an expected number of assertions helps to avoid false test passes, so be sure to use the test.expect() method at the start of your test functions, and test.done() when finished.

Running Tests

nodeunit comes with a basic command-line test runner, which exists in the lib folder. Example usage:

node nodeunit/lib/testrunner.js testmodule1.js testfolder [...]

The testrunner uses color output, because I think that's more fun :) I intend to add a no-color option in future. To give you a feeling of the fun you'll be having writing tests, lets fix the example at the start of the README:

Ahhh, Doesn't that feel better?

You can also add some code to the bottom of your test modules so they can be run directly from the command-line:

if(module.id == '.'){
    var testrunner = require('nodeunit').testrunner;

NOTE: this requires nodeunit to be in your require paths. You can make nodeunit available to all your projects by copying it to ~/.node-libraries

When using the included test runner, it will exit using the failed number of assertions as the exit code. Exiting with 0 when all tests pass.

Adding nodeunit to Your Projects

Usually, you'll want to create a script that runs the tests for your project with the correct require paths set up. Here's an example test script, with deps, lib and test directories:


require.paths.push(__dirname + '/deps');
require.paths.push(__dirname + '/lib');
var testrunner = require('nodeunit').testrunner;


If you're using git, you might find it useful to include nodeunit as a submodule. Using submodules makes it easy for developers to download nodeunit and run your test suite, without cluttering up your repository with the source code. To add nodeunit as a git submodule do the following:

git submodule add git://github.com/caolan/nodeunit.git deps/nodeunit

This will add nodeunit to the deps folder of your project. Now, when cloning the repository, nodeunit can be downloaded by doing the following:

git submodule init
git submodule update

Let's update the test script above with a helpful hint on how to get nodeunit, if its missing:


require.paths.push(__dirname + '/deps');
require.paths.push(__dirname + '/lib');

try {
    var testrunner = require('nodeunit').testrunner;
catch(e) {
    var sys = require('sys');
    sys.puts("Cannot find nodeunit module.");
    sys.puts("You can download submodules for this project by doing:");
    sys.puts("    git submodule init");
    sys.puts("    git submodule update");


Now if someone attempts to run your test suite without nodeunit installed they will be prompted to download the submodules for your project.

Writing a Test Runner

nodeunit exports runTest(fn, options), runModule(mod, options) and runFiles(paths, options). You'll most likely want to run test suites from files, which can be done using the latter function. The options argument can contain callbacks which run during testing. nodeunit provides the following callbacks:

  • moduleStart(name) - called before a module is tested
  • moduleDone(name, assertions) - called once all test functions within the module have completed (see assertions object reference below) ALL tests within the module
  • testStart(name) - called before a test function is run
  • testDone(name, assertions) - called once a test function has completed (by calling test.done())
  • log(assertion) - called whenever an assertion is made (see assertion object reference below)
  • done(assertions) - called after all tests/modules are complete

The assertion object:

  • passed() - did the assertion pass?
  • failed() - did the assertion fail?
  • error - the AssertionError if the assertion failed
  • method - the nodeunit assertion method used (ok, same, equals...)
  • message - the message the assertion method was called with (optional)

The assertions object:

  • An array-like object with the following new attributes:
    • failures - the number of assertions which failed
    • duration - the time taken for the test to complete in msecs

For a reference implementation of a test runner, see lib/testrunner.js in the nodeunit project directory.

Running the nodeunit Tests

The tests for nodeunit are written using nodeunit itself as the test framework. However, the module test-base.js first does some basic tests using the assert module to ensure that test functions are actually run, and a basic level of nodeunit functionality is available.

To run the nodeunit tests do: node test.js