only tests#

If Node.js is started with the --test-only command-line option, or test isolation is disabled, it is possible to skip all tests except for a selected subset by passing the only option to the tests that should run. When a test with the only option is set, all subtests are also run. If a suite has the only option set, all tests within the suite are run, unless it has descendants with the only option set, in which case only those tests are run.

When using subtests within a test()/it(), it is required to mark all ancestor tests with the only option to run only a selected subset of tests.

The test context’s runOnly() method can be used to implement the same behavior at the subtest level. Tests that are not executed are omitted from the test runner output.

// Assume Node.js is run with the --test-only command-line option.
// The suite's 'only' option is set, so these tests are run.
test('this test is run', { only: true }, async (t) => {
  // Within this test, all subtests are run by default.
  await t.test('running subtest');

  // The test context can be updated to run subtests with the 'only' option.
  t.runOnly(true);
  await t.test('this subtest is now skipped');
  await t.test('this subtest is run', { only: true });

  // Switch the context back to execute all tests.
  t.runOnly(false);
  await t.test('this subtest is now run');

  // Explicitly do not run these tests.
  await t.test('skipped subtest 3', { only: false });
  await t.test('skipped subtest 4', { skip: true });
});

// The 'only' option is not set, so this test is skipped.
test('this test is not run', () => {
  // This code is not run.
  throw new Error('fail');
});

describe('a suite', () => {
  // The 'only' option is set, so this test is run.
  it('this test is run', { only: true }, () => {
    // This code is run.
  });

  it('this test is not run', () => {
    // This code is not run.
    throw new Error('fail');
  });
});

describe.only('a suite', () => {
  // The 'only' option is set, so this test is run.
  it('this test is run', () => {
    // This code is run.
  });

  it('this test is run', () => {
    // This code is run.
  });
});
copy

Filtering tests by name#

The --test-name-pattern command-line option can be used to only run tests whose name matches the provided pattern, and the --test-skip-pattern option can be used to skip tests whose name matches the provided pattern. Test name patterns are interpreted as JavaScript regular expressions. The --test-name-pattern and --test-skip-pattern options can be specified multiple times in order to run nested tests. For each test that is executed, any corresponding test hooks, such as beforeEach(), are also run. Tests that are not executed are omitted from the test runner output.

Given the following test file, starting Node.js with the --test-name-pattern="test [1-3]" option would cause the test runner to execute test 1, test 2, and test 3. If test 1 did not match the test name pattern, then its subtests would not execute, despite matching the pattern. The same set of tests could also be executed by passing --test-name-pattern multiple times (e.g. --test-name-pattern="test 1", --test-name-pattern="test 2", etc.).

test('test 1', async (t) => {
  await t.test('test 2');
  await t.test('test 3');
});

test('Test 4', async (t) => {
  await t.test('Test 5');
  await t.test('test 6');
});
copy

Test name patterns can also be specified using regular expression literals. This allows regular expression flags to be used. In the previous example, starting Node.js with --test-name-pattern="/test [4-5]/i" (or --test-skip-pattern="/test [4-5]/i") would match Test 4 and Test 5 because the pattern is case-insensitive.

To match a single test with a pattern, you can prefix it with all its ancestor test names separated by space, to ensure it is unique. For example, given the following test file:

describe('test 1', (t) => {
  it('some test');
});

describe('test 2', (t) => {
  it('some test');
});
copy

Starting Node.js with --test-name-pattern="test 1 some test" would match only some test in test 1.

Test name patterns do not change the set of files that the test runner executes.

If both --test-name-pattern and --test-skip-pattern are supplied, tests must satisfy both requirements in order to be executed.

Extraneous asynchronous activity#

Once a test function finishes executing, the results are reported as quickly as possible while maintaining the order of the tests. However, it is possible for the test function to generate asynchronous activity that outlives the test itself. The test runner handles this type of activity, but does not delay the reporting of test results in order to accommodate it.

In the following example, a test completes with two setImmediate() operations still outstanding. The first setImmediate() attempts to create a new subtest. Because the parent test has already finished and output its results, the new subtest is immediately marked as failed, and reported later to the <TestsStream>.

The second setImmediate() creates an uncaughtException event. uncaughtException and unhandledRejection events originating from a completed test are marked as failed by the test module and reported as diagnostic warnings at the top level by the <TestsStream>.

test('a test that creates asynchronous activity', (t) => {
  setImmediate(() => {
    t.test('subtest that is created too late', (t) => {
      throw new Error('error1');
    });
  });

  setImmediate(() => {
    throw new Error('error2');
  });

  // The test finishes after this line.
});
copy

Watch mode#

The Node.js test runner supports running in watch mode by passing the --watch flag:

node --test --watch
copy

In watch mode, the test runner will watch for changes to test files and their dependencies. When a change is detected, the test runner will rerun the tests affected by the change. The test runner will continue to run until the process is terminated.

Global setup and teardown#

The test runner supports specifying a module that will be evaluated before all tests are executed and can be used to setup global state or fixtures for tests. This is useful for preparing resources or setting up shared state that is required by multiple tests.

This module can export any of the following:

• A globalSetup function which runs once before all tests start
• A globalTeardown function which runs once after all tests complete

The module is specified using the --test-global-setup flag when running tests from the command line.

// setup-module.js
async function globalSetup() {
  // Setup shared resources, state, or environment
  console.log('Global setup executed');
  // Run servers, create files, prepare databases, etc.
}

async function globalTeardown() {
  // Clean up resources, state, or environment
  console.log('Global teardown executed');
  // Close servers, remove files, disconnect from databases, etc.
}

module.exports = { globalSetup, globalTeardown };
// setup-module.mjs
export async function globalSetup() {
  // Setup shared resources, state, or environment
  console.log('Global setup executed');
  // Run servers, create files, prepare databases, etc.
}

export async function globalTeardown() {
  // Clean up resources, state, or environment
  console.log('Global teardown executed');
  // Close servers, remove files, disconnect from databases, etc.
}
copy

If the global setup function throws an error, no tests will be run and the process will exit with a non-zero exit code. The global teardown function will not be called in this case.

Running tests from the command line#

The Node.js test runner can be invoked from the command line by passing the --test flag:

node --test
copy

By default, Node.js will run all files matching these patterns:

• **/*.test.{cjs,mjs,js}
• **/*-test.{cjs,mjs,js}
• **/*_test.{cjs,mjs,js}
• **/test-*.{cjs,mjs,js}
• **/test.{cjs,mjs,js}
• **/test/**/*.{cjs,mjs,js}

Unless --no-strip-types is supplied, the following additional patterns are also matched:

• **/*.test.{cts,mts,ts}
• **/*-test.{cts,mts,ts}
• **/*_test.{cts,mts,ts}
• **/test-*.{cts,mts,ts}
• **/test.{cts,mts,ts}
• **/test/**/*.{cts,mts,ts}

Alternatively, one or more glob patterns can be provided as the final argument(s) to the Node.js command, as shown below. Glob patterns follow the behavior of glob(7). The glob patterns should be enclosed in double quotes on the command line to prevent shell expansion, which can reduce portability across systems.

node --test "**/*.test.js" "**/*.spec.js"
copy

Matching files are executed as test files. More information on the test file execution can be found in the test runner execution model section.

Test runner execution model#

When process-level test isolation is enabled, each matching test file is executed in a separate child process. The maximum number of child processes running at any time is controlled by the --test-concurrency flag. If the child process finishes with an exit code of 0, the test is considered passing. Otherwise, the test is considered to be a failure. Test files must be executable by Node.js, but are not required to use the node:test module internally.

Each test file is executed as if it was a regular script. That is, if the test file itself uses node:test to define tests, all of those tests will be executed within a single application thread, regardless of the value of the concurrency option of test().

When process-level test isolation is disabled, each matching test file is imported into the test runner process. Once all test files have been loaded, the top level tests are executed with a concurrency of one. Because the test files are all run within the same context, it is possible for tests to interact with each other in ways that are not possible when isolation is enabled. For example, if a test relies on global state, it is possible for that state to be modified by a test originating from another file.

Child process option inheritance#

When running tests in process isolation mode (the default), spawned child processes inherit Node.js options from the parent process, including those specified in configuration files. However, certain flags are filtered out to enable proper test runner functionality:

• --test – Prevented to avoid recursive test execution
• --experimental-test-coverage – Managed by the test runner
• --watch – Watch mode is handled at the parent level
• --experimental-default-config-file – Config file loading is handled by the parent
• --test-reporter – Reporting is managed by the parent process
• --test-reporter-destination – Output destinations are controlled by the parent
• --experimental-config-file – Config file paths are managed by the parent

All other Node.js options from command line arguments, environment variables, and configuration files are inherited by the child processes.

Collecting code coverage#

When Node.js is started with the --experimental-test-coverage command-line flag, code coverage is collected and statistics are reported once all tests have completed. If the NODE_V8_COVERAGE environment variable is used to specify a code coverage directory, the generated V8 coverage files are written to that directory. Node.js core modules and files within node_modules/ directories are, by default, not included in the coverage report. However, they can be explicitly included via the --test-coverage-include flag. By default all the matching test files are excluded from the coverage report. Exclusions can be overridden by using the --test-coverage-exclude flag. If coverage is enabled, the coverage report is sent to any test reporters via the 'test:coverage' event.

Coverage can be disabled on a series of lines using the following comment syntax:

/* node:coverage disable */
if (anAlwaysFalseCondition) {
  // Code in this branch will never be executed, but the lines are ignored for
  // coverage purposes. All lines following the 'disable' comment are ignored
  // until a corresponding 'enable' comment is encountered.
  console.log('this is never executed');
}
/* node:coverage enable */
copy

Coverage can also be disabled for a specified number of lines. After the specified number of lines, coverage will be automatically reenabled. If the number of lines is not explicitly provided, a single line is ignored.

/* node:coverage ignore next */
if (anAlwaysFalseCondition) { console.log('this is never executed'); }

/* node:coverage ignore next 3 */
if (anAlwaysFalseCondition) {
  console.log('this is never executed');
}
copy

Coverage reporters#

The tap and spec reporters will print a summary of the coverage statistics. There is also an lcov reporter that will generate an lcov file which can be used as an in depth coverage report.

node --test --experimental-test-coverage --test-reporter=lcov --test-reporter-destination=lcov.info
copy

• No test results are reported by this reporter.
• This reporter should ideally be used alongside another reporter.

Mocking#

The node:test module supports mocking during testing via a top-level mock object. The following example creates a spy on a function that adds two numbers together. The spy is then used to assert that the function was called as expected.

import assert from 'node:assert';
import { mock, test } from 'node:test';

test('spies on a function', () => {
  const sum = mock.fn((a, b) => {
    return a + b;
  });

  assert.strictEqual(sum.mock.callCount(), 0);
  assert.strictEqual(sum(3, 4), 7);
  assert.strictEqual(sum.mock.callCount(), 1);

  const call = sum.mock.calls[0];
  assert.deepStrictEqual(call.arguments, [3, 4]);
  assert.strictEqual(call.result, 7);
  assert.strictEqual(call.error, undefined);

  // Reset the globally tracked mocks.
  mock.reset();
});
'use strict';
const assert = require('node:assert');
const { mock, test } = require('node:test');

test('spies on a function', () => {
  const sum = mock.fn((a, b) => {
    return a + b;
  });

  assert.strictEqual(sum.mock.callCount(), 0);
  assert.strictEqual(sum(3, 4), 7);
  assert.strictEqual(sum.mock.callCount(), 1);

  const call = sum.mock.calls[0];
  assert.deepStrictEqual(call.arguments, [3, 4]);
  assert.strictEqual(call.result, 7);
  assert.strictEqual(call.error, undefined);

  // Reset the globally tracked mocks.
  mock.reset();
});
copy

The same mocking functionality is also exposed on the TestContext object of each test. The following example creates a spy on an object method using the API exposed on the TestContext. The benefit of mocking via the test context is that the test runner will automatically restore all mocked functionality once the test finishes.

test('spies on an object method', (t) => {
  const number = {
    value: 5,
    add(a) {
      return this.value + a;
    },
  };

  t.mock.method(number, 'add');
  assert.strictEqual(number.add.mock.callCount(), 0);
  assert.strictEqual(number.add(3), 8);
  assert.strictEqual(number.add.mock.callCount(), 1);

  const call = number.add.mock.calls[0];

  assert.deepStrictEqual(call.arguments, [3]);
  assert.strictEqual(call.result, 8);
  assert.strictEqual(call.target, undefined);
  assert.strictEqual(call.this, number);
});
copy

Timers#

Mocking timers is a technique commonly used in software testing to simulate and control the behavior of timers, such as setInterval and setTimeout, without actually waiting for the specified time intervals.

Refer to the MockTimers class for a full list of methods and features.

This allows developers to write more reliable and predictable tests for time-dependent functionality.

The example below shows how to mock setTimeout. Using .enable({ apis: ['setTimeout'] }); it will mock the setTimeout functions in the node:timers and node:timers/promises modules, as well as from the Node.js global context.

Note: Destructuring functions such as import { setTimeout } from 'node:timers' is currently not supported by this API.

import assert from 'node:assert';
import { mock, test } from 'node:test';

test('mocks setTimeout to be executed synchronously without having to actually wait for it', () => {
  const fn = mock.fn();

  // Optionally choose what to mock
  mock.timers.enable({ apis: ['setTimeout'] });
  setTimeout(fn, 9999);
  assert.strictEqual(fn.mock.callCount(), 0);

  // Advance in time
  mock.timers.tick(9999);
  assert.strictEqual(fn.mock.callCount(), 1);

  // Reset the globally tracked mocks.
  mock.timers.reset();

  // If you call reset mock instance, it will also reset timers instance
  mock.reset();
});
const assert = require('node:assert');
const { mock, test } = require('node:test');

test('mocks setTimeout to be executed synchronously without having to actually wait for it', () => {
  const fn = mock.fn();

  // Optionally choose what to mock
  mock.timers.enable({ apis: ['setTimeout'] });
  setTimeout(fn, 9999);
  assert.strictEqual(fn.mock.callCount(), 0);

  // Advance in time
  mock.timers.tick(9999);
  assert.strictEqual(fn.mock.callCount(), 1);

  // Reset the globally tracked mocks.
  mock.timers.reset();

  // If you call reset mock instance, it will also reset timers instance
  mock.reset();
});
copy

The same mocking functionality is also exposed in the mock property on the TestContext object of each test. The benefit of mocking via the test context is that the test runner will automatically restore all mocked timers functionality once the test finishes.

import assert from 'node:assert';
import { test } from 'node:test';

test('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {
  const fn = context.mock.fn();

  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['setTimeout'] });
  setTimeout(fn, 9999);
  assert.strictEqual(fn.mock.callCount(), 0);

  // Advance in time
  context.mock.timers.tick(9999);
  assert.strictEqual(fn.mock.callCount(), 1);
});
const assert = require('node:assert');
const { test } = require('node:test');

test('mocks setTimeout to be executed synchronously without having to actually wait for it', (context) => {
  const fn = context.mock.fn();

  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['setTimeout'] });
  setTimeout(fn, 9999);
  assert.strictEqual(fn.mock.callCount(), 0);

  // Advance in time
  context.mock.timers.tick(9999);
  assert.strictEqual(fn.mock.callCount(), 1);
});
copy

Dates#

The mock timers API also allows the mocking of the Date object. This is a useful feature for testing time-dependent functionality, or to simulate internal calendar functions such as Date.now().

The dates implementation is also part of the MockTimers class. Refer to it for a full list of methods and features.

Note: Dates and timers are dependent when mocked together. This means that if you have both the Date and setTimeout mocked, advancing the time will also advance the mocked date as they simulate a single internal clock.

The example below show how to mock the Date object and obtain the current Date.now() value.

import assert from 'node:assert';
import { test } from 'node:test';

test('mocks the Date object', (context) => {
  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['Date'] });
  // If not specified, the initial date will be based on 0 in the UNIX epoch
  assert.strictEqual(Date.now(), 0);

  // Advance in time will also advance the date
  context.mock.timers.tick(9999);
  assert.strictEqual(Date.now(), 9999);
});
const assert = require('node:assert');
const { test } = require('node:test');

test('mocks the Date object', (context) => {
  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['Date'] });
  // If not specified, the initial date will be based on 0 in the UNIX epoch
  assert.strictEqual(Date.now(), 0);

  // Advance in time will also advance the date
  context.mock.timers.tick(9999);
  assert.strictEqual(Date.now(), 9999);
});
copy

If there is no initial epoch set, the initial date will be based on 0 in the Unix epoch. This is January 1st, 1970, 00:00:00 UTC. You can set an initial date by passing a now property to the .enable() method. This value will be used as the initial date for the mocked Date object. It can either be a positive integer, or another Date object.

import assert from 'node:assert';
import { test } from 'node:test';

test('mocks the Date object with initial time', (context) => {
  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['Date'], now: 100 });
  assert.strictEqual(Date.now(), 100);

  // Advance in time will also advance the date
  context.mock.timers.tick(200);
  assert.strictEqual(Date.now(), 300);
});
const assert = require('node:assert');
const { test } = require('node:test');

test('mocks the Date object with initial time', (context) => {
  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['Date'], now: 100 });
  assert.strictEqual(Date.now(), 100);

  // Advance in time will also advance the date
  context.mock.timers.tick(200);
  assert.strictEqual(Date.now(), 300);
});
copy

You can use the .setTime() method to manually move the mocked date to another time. This method only accepts a positive integer.

Note: This method will not execute any mocked timers that are in the past from the new time.

In the below example we are setting a new time for the mocked date.

import assert from 'node:assert';
import { test } from 'node:test';

test('sets the time of a date object', (context) => {
  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['Date'], now: 100 });
  assert.strictEqual(Date.now(), 100);

  // Advance in time will also advance the date
  context.mock.timers.setTime(1000);
  context.mock.timers.tick(200);
  assert.strictEqual(Date.now(), 1200);
});
const assert = require('node:assert');
const { test } = require('node:test');

test('sets the time of a date object', (context) => {
  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['Date'], now: 100 });
  assert.strictEqual(Date.now(), 100);

  // Advance in time will also advance the date
  context.mock.timers.setTime(1000);
  context.mock.timers.tick(200);
  assert.strictEqual(Date.now(), 1200);
});
copy

Timers scheduled in the past will not run when you call setTime(). To execute those timers, you can use the .tick() method to move forward from the new time.

import assert from 'node:assert';
import { test } from 'node:test';

test('setTime does not execute timers', (context) => {
  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });
  const fn = context.mock.fn();
  setTimeout(fn, 1000);

  context.mock.timers.setTime(800);
  // Timer is not executed as the time is not yet reached
  assert.strictEqual(fn.mock.callCount(), 0);
  assert.strictEqual(Date.now(), 800);

  context.mock.timers.setTime(1200);
  // Timer is still not executed
  assert.strictEqual(fn.mock.callCount(), 0);
  // Advance in time to execute the timer
  context.mock.timers.tick(0);
  assert.strictEqual(fn.mock.callCount(), 1);
  assert.strictEqual(Date.now(), 1200);
});
const assert = require('node:assert');
const { test } = require('node:test');

test('runs timers as setTime passes ticks', (context) => {
  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });
  const fn = context.mock.fn();
  setTimeout(fn, 1000);

  context.mock.timers.setTime(800);
  // Timer is not executed as the time is not yet reached
  assert.strictEqual(fn.mock.callCount(), 0);
  assert.strictEqual(Date.now(), 800);

  context.mock.timers.setTime(1200);
  // Timer is executed as the time is now reached
  assert.strictEqual(fn.mock.callCount(), 1);
  assert.strictEqual(Date.now(), 1200);
});
copy

Using .runAll() will execute all timers that are currently in the queue. This will also advance the mocked date to the time of the last timer that was executed as if the time has passed.

import assert from 'node:assert';
import { test } from 'node:test';

test('runs timers as setTime passes ticks', (context) => {
  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });
  const fn = context.mock.fn();
  setTimeout(fn, 1000);
  setTimeout(fn, 2000);
  setTimeout(fn, 3000);

  context.mock.timers.runAll();
  // All timers are executed as the time is now reached
  assert.strictEqual(fn.mock.callCount(), 3);
  assert.strictEqual(Date.now(), 3000);
});
const assert = require('node:assert');
const { test } = require('node:test');

test('runs timers as setTime passes ticks', (context) => {
  // Optionally choose what to mock
  context.mock.timers.enable({ apis: ['setTimeout', 'Date'] });
  const fn = context.mock.fn();
  setTimeout(fn, 1000);
  setTimeout(fn, 2000);
  setTimeout(fn, 3000);

  context.mock.timers.runAll();
  // All timers are executed as the time is now reached
  assert.strictEqual(fn.mock.callCount(), 3);
  assert.strictEqual(Date.now(), 3000);
});
copy

Snapshot testing#

Snapshot tests allow arbitrary values to be serialized into string values and compared against a set of known good values. The known good values are known as snapshots, and are stored in a snapshot file. Snapshot files are managed by the test runner, but are designed to be human readable to aid in debugging. Best practice is for snapshot files to be checked into source control along with your test files.

Snapshot files are generated by starting Node.js with the --test-update-snapshots command-line flag. A separate snapshot file is generated for each test file. By default, the snapshot file has the same name as the test file with a .snapshot file extension. This behavior can be configured using the snapshot.setResolveSnapshotPath() function. Each snapshot assertion corresponds to an export in the snapshot file.

An example snapshot test is shown below. The first time this test is executed, it will fail because the corresponding snapshot file does not exist.

// test.js
suite('suite of snapshot tests', () => {
  test('snapshot test', (t) => {
    t.assert.snapshot({ value1: 1, value2: 2 });
    t.assert.snapshot(5);
  });
});
copy

Generate the snapshot file by running the test file with --test-update-snapshots. The test should pass, and a file named test.js.snapshot is created in the same directory as the test file. The contents of the snapshot file are shown below. Each snapshot is identified by the full name of test and a counter to differentiate between snapshots in the same test.

exports[`suite of snapshot tests > snapshot test 1`] = `
{
  "value1": 1,
  "value2": 2
}
`;

exports[`suite of snapshot tests > snapshot test 2`] = `
5
`;
copy

Once the snapshot file is created, run the tests again without the --test-update-snapshots flag. The tests should pass now.

Test reporters#

The node:test module supports passing --test-reporter flags for the test runner to use a specific reporter.

The following built-reporters are supported:

• spec The spec reporter outputs the test results in a human-readable format. This is the default reporter.

• tap The tap reporter outputs the test results in the TAP format.

• dot The dot reporter outputs the test results in a compact format, where each passing test is represented by a ., and each failing test is represented by a X.

• junit The junit reporter outputs test results in a jUnit XML format

• lcov The lcov reporter outputs test coverage when used with the --experimental-test-coverage flag.

The exact output of these reporters is subject to change between versions of Node.js, and should not be relied on programmatically. If programmatic access to the test runner’s output is required, use the events emitted by the <TestsStream>.

The reporters are available via the node:test/reporters module:

import { tap, spec, dot, junit, lcov } from 'node:test/reporters';
const { tap, spec, dot, junit, lcov } = require('node:test/reporters');
copy

Custom reporters#

--test-reporter can be used to specify a path to custom reporter. A custom reporter is a module that exports a value accepted by stream.compose. Reporters should transform events emitted by a <TestsStream>

Example of a custom reporter using <stream.Transform>:

import { Transform } from 'node:stream';

const customReporter = new Transform({
  writableObjectMode: true,
  transform(event, encoding, callback) {
    switch (event.type) {
      case 'test:dequeue':
        callback(null, `test ${event.data.name} dequeued`);
        break;
      case 'test:enqueue':
        callback(null, `test ${event.data.name} enqueued`);
        break;
      case 'test:watch:drained':
        callback(null, 'test watch queue drained');
        break;
      case 'test:watch:restarted':
        callback(null, 'test watch restarted due to file change');
        break;
      case 'test:start':
        callback(null, `test ${event.data.name} started`);
        break;
      case 'test:pass':
        callback(null, `test ${event.data.name} passed`);
        break;
      case 'test:fail':
        callback(null, `test ${event.data.name} failed`);
        break;
      case 'test:plan':
        callback(null, 'test plan');
        break;
      case 'test:diagnostic':
      case 'test:stderr':
      case 'test:stdout':
        callback(null, event.data.message);
        break;
      case 'test:coverage': {
        const { totalLineCount } = event.data.summary.totals;
        callback(null, `total line count: ${totalLineCount}\n`);
        break;
      }
    }
  },
});

export default customReporter;
const { Transform } = require('node:stream');

const customReporter = new Transform({
  writableObjectMode: true,
  transform(event, encoding, callback) {
    switch (event.type) {
      case 'test:dequeue':
        callback(null, `test ${event.data.name} dequeued`);
        break;
      case 'test:enqueue':
        callback(null, `test ${event.data.name} enqueued`);
        break;
      case 'test:watch:drained':
        callback(null, 'test watch queue drained');
        break;
      case 'test:watch:restarted':
        callback(null, 'test watch restarted due to file change');
        break;
      case 'test:start':
        callback(null, `test ${event.data.name} started`);
        break;
      case 'test:pass':
        callback(null, `test ${event.data.name} passed`);
        break;
      case 'test:fail':
        callback(null, `test ${event.data.name} failed`);
        break;
      case 'test:plan':
        callback(null, 'test plan');
        break;
      case 'test:diagnostic':
      case 'test:stderr':
      case 'test:stdout':
        callback(null, event.data.message);
        break;
      case 'test:coverage': {
        const { totalLineCount } = event.data.summary.totals;
        callback(null, `total line count: ${totalLineCount}\n`);
        break;
      }
    }
  },
});

module.exports = customReporter;
copy

Example of a custom reporter using a generator function:

export default async function * customReporter(source) {
  for await (const event of source) {
    switch (event.type) {
      case 'test:dequeue':
        yield `test ${event.data.name} dequeued\n`;
        break;
      case 'test:enqueue':
        yield `test ${event.data.name} enqueued\n`;
        break;
      case 'test:watch:drained':
        yield 'test watch queue drained\n';
        break;
      case 'test:watch:restarted':
        yield 'test watch restarted due to file change\n';
        break;
      case 'test:start':
        yield `test ${event.data.name} started\n`;
        break;
      case 'test:pass':
        yield `test ${event.data.name} passed\n`;
        break;
      case 'test:fail':
        yield `test ${event.data.name} failed\n`;
        break;
      case 'test:plan':
        yield 'test plan\n';
        break;
      case 'test:diagnostic':
      case 'test:stderr':
      case 'test:stdout':
        yield `${event.data.message}\n`;
        break;
      case 'test:coverage': {
        const { totalLineCount } = event.data.summary.totals;
        yield `total line count: ${totalLineCount}\n`;
        break;
      }
    }
  }
}
module.exports = async function * customReporter(source) {
  for await (const event of source) {
    switch (event.type) {
      case 'test:dequeue':
        yield `test ${event.data.name} dequeued\n`;
        break;
      case 'test:enqueue':
        yield `test ${event.data.name} enqueued\n`;
        break;
      case 'test:watch:drained':
        yield 'test watch queue drained\n';
        break;
      case 'test:watch:restarted':
        yield 'test watch restarted due to file change\n';
        break;
      case 'test:start':
        yield `test ${event.data.name} started\n`;
        break;
      case 'test:pass':
        yield `test ${event.data.name} passed\n`;
        break;
      case 'test:fail':
        yield `test ${event.data.name} failed\n`;
        break;
      case 'test:plan':
        yield 'test plan\n';
        break;
      case 'test:diagnostic':
      case 'test:stderr':
      case 'test:stdout':
        yield `${event.data.message}\n`;
        break;
      case 'test:coverage': {
        const { totalLineCount } = event.data.summary.totals;
        yield `total line count: ${totalLineCount}\n`;
        break;
      }
    }
  }
};
copy

The value provided to --test-reporter should be a string like one used in an import() in JavaScript code, or a value provided for --import.

Multiple reporters#

The --test-reporter flag can be specified multiple times to report test results in several formats. In this situation it is required to specify a destination for each reporter using --test-reporter-destination. Destination can be stdout, stderr, or a file path. Reporters and destinations are paired according to the order they were specified.

In the following example, the spec reporter will output to stdout, and the dot reporter will output to file.txt:

node --test-reporter=spec --test-reporter=dot --test-reporter-destination=stdout --test-reporter-destination=file.txt
copy

When a single reporter is specified, the destination will default to stdout, unless a destination is explicitly provided.

run([options])#

• options <Object> Configuration options for running tests. The following properties are supported:
  • concurrency <number> | <boolean> If a number is provided, then that many test processes would run in parallel, where each process corresponds to one test file. If true, it would run os.availableParallelism() - 1 test files in parallel. If false, it would only run one test file at a time. Default: false.
  • cwd <string> Specifies the current working directory to be used by the test runner. Serves as the base path for resolving files as if running tests from the command line from that directory. Default: process.cwd().
  • files <Array> An array containing the list of files to run. Default: Same as running tests from the command line.
  • forceExit <boolean> Configures the test runner to exit the process once all known tests have finished executing even if the event loop would otherwise remain active. Default: false.
  • globPatterns <Array> An array containing the list of glob patterns to match test files. This option cannot be used together with files. Default: Same as running tests from the command line.
  • inspectPort <number> | <Function> Sets inspector port of test child process. This can be a number, or a function that takes no arguments and returns a number. If a nullish value is provided, each process gets its own port, incremented from the primary’s process.debugPort. This option is ignored if the isolation option is set to 'none' as no child processes are spawned. Default: undefined.
  • isolation <string> Configures the type of test isolation. If set to 'process', each test file is run in a separate child process. If set to 'none', all test files run in the current process. Default: 'process'.
  • only <boolean> If truthy, the test context will only run tests that have the only option set
  • setup <Function> A function that accepts the TestsStream instance and can be used to setup listeners before any tests are run. Default: undefined.
  • execArgv <Array> An array of CLI flags to pass to the node executable when spawning the subprocesses. This option has no effect when isolation is 'none‘. Default: []
  • argv <Array> An array of CLI flags to pass to each test file when spawning the subprocesses. This option has no effect when isolation is 'none'. Default: [].
  • signal <AbortSignal> Allows aborting an in-progress test execution.
  • testNamePatterns <string> | <RegExp> | <Array> A String, RegExp or a RegExp Array, that can be used to only run tests whose name matches the provided pattern. Test name patterns are interpreted as JavaScript regular expressions. For each test that is executed, any corresponding test hooks, such as beforeEach(), are also run. Default: undefined.
  • testSkipPatterns <string> | <RegExp> | <Array> A String, RegExp or a RegExp Array, that can be used to exclude running tests whose name matches the provided pattern. Test name patterns are interpreted as JavaScript regular expressions. For each test that is executed, any corresponding test hooks, such as beforeEach(), are also run. Default: undefined.
  • timeout <number> A number of milliseconds the test execution will fail after. If unspecified, subtests inherit this value from their parent. Default: Infinity.
  • watch <boolean> Whether to run in watch mode or not. Default: false.
  • shard <Object> Running tests in a specific shard. Default: undefined.
    • index <number> is a positive integer between 1 and <total> that specifies the index of the shard to run. This option is required.
    • total <number> is a positive integer that specifies the total number of shards to split the test files to. This option is required.
  • rerunFailuresFilePath <string> A file path where the test runner will store the state of the tests to allow rerunning only the failed tests on a next run. see [Rerunning failed tests][] for more information. Default: undefined.
  • coverage <boolean> enable code coverage collection. Default: false.
  • coverageExcludeGlobs <string> | <Array> Excludes specific files from code coverage using a glob pattern, which can match both absolute and relative file paths. This property is only applicable when coverage was set to true. If both coverageExcludeGlobs and coverageIncludeGlobs are provided, files must meet both criteria to be included in the coverage report. Default: undefined.
  • coverageIncludeGlobs <string> | <Array> Includes specific files in code coverage using a glob pattern, which can match both absolute and relative file paths. This property is only applicable when coverage was set to true. If both coverageExcludeGlobs and coverageIncludeGlobs are provided, files must meet both criteria to be included in the coverage report. Default: undefined.
  • lineCoverage <number> Require a minimum percent of covered lines. If code coverage does not reach the threshold specified, the process will exit with code 1. Default: 0.
  • branchCoverage <number> Require a minimum percent of covered branches. If code coverage does not reach the threshold specified, the process will exit with code 1. Default: 0.
  • functionCoverage <number> Require a minimum percent of covered functions. If code coverage does not reach the threshold specified, the process will exit with code 1. Default: 0.
  • env <Object> Specify environment variables to be passed along to the test process. This options is not compatible with isolation='none'. These variables will override those from the main process, and are not merged with process.env. Default: process.env.
• Returns: <TestsStream>

Note: shard is used to horizontally parallelize test running across machines or processes, ideal for large-scale executions across varied environments. It’s incompatible with watch mode, tailored for rapid code iteration by automatically rerunning tests on file changes.

import { tap } from 'node:test/reporters';
import { run } from 'node:test';
import process from 'node:process';
import path from 'node:path';

run({ files: [path.resolve('./tests/test.js')] })
 .on('test:fail', () => {
   process.exitCode = 1;
 })
 .compose(tap)
 .pipe(process.stdout);
const { tap } = require('node:test/reporters');
const { run } = require('node:test');
const path = require('node:path');

run({ files: [path.resolve('./tests/test.js')] })
 .on('test:fail', () => {
   process.exitCode = 1;
 })
 .compose(tap)
 .pipe(process.stdout);
copy

suite([name][, options][, fn])#

• name <string> The name of the suite, which is displayed when reporting test results. Default: The name property of fn, or '<anonymous>' if fn does not have a name.
• options <Object> Optional configuration options for the suite. This supports the same options as test([name][, options][, fn]).
• fn <Function> | <AsyncFunction> The suite function declaring nested tests and suites. The first argument to this function is a SuiteContext object. Default: A no-op function.
• Returns: <Promise> Immediately fulfilled with undefined.

The suite() function is imported from the node:test module.

suite.skip([name][, options][, fn])#

Shorthand for skipping a suite. This is the same as suite([name], { skip: true }[, fn]).

suite.todo([name][, options][, fn])#

Shorthand for marking a suite as TODO. This is the same as suite([name], { todo: true }[, fn]).

suite.only([name][, options][, fn])#

Shorthand for marking a suite as only. This is the same as suite([name], { only: true }[, fn]).

test([name][, options][, fn])#

• name <string> The name of the test, which is displayed when reporting test results. Default: The name property of fn, or '<anonymous>' if fn does not have a name.
• options <Object> Configuration options for the test. The following properties are supported:
  • concurrency <number> | <boolean> If a number is provided, then that many tests would run asynchronously (they are still managed by the single-threaded event loop). If true, all scheduled asynchronous tests run concurrently within the thread. If false, only one test runs at a time. If unspecified, subtests inherit this value from their parent. Default: false.
  • expectFailure <boolean> | <string> | <RegExp> | <Function> | <Object> | <Error> If truthy, the test is expected to fail. If a non-empty string is provided, that string is displayed in the test results as the reason why the test is expected to fail. If a , ,