9.0.0 / 2021-06-07

:boom: Breaking Changes

• #4633: Drop Node.js v10.x support (@juergba)

• #4635: import-first loading of test files (@giltayar)

Mocha is going ESM-first! This means that it will now use ESM import(test_file) to load the test files, instead of the CommonJS require(test_file). This is not a problem, as import can also load most files that require does. In the rare cases where this fails, it will fallback to require(...). This ESM-first approach is the next step in Mocha's ESM migration, and allows ESM loaders to load and transform the test file.

• #4636: Remove deprecated utils.lookupFiles() (@juergba)

• #4638: Limit the size of actual/expected for diff generation (@juergba)

• #4389: Refactoring: Consuming log-symbols alternate to code for win32 in reporters/base (@MoonSupport)

:tada: Enhancements

• #4640: Add new option --dry-run (@juergba)

:bug: Fixes

• #4128: Fix: control stringification of error message (@syeutyu)

:nut_and_bolt: Other

• #4646: Deprecate Runner(suite: Suite, delay: boolean) signature (@juergba)
• #4643: Update production dependencies (@juergba)

8.4.0 / 2021-05-07

:tada: Enhancements

• #4502: CLI file parsing errors now have error codes (@evaline-ju)

:bug: Fixes

• #4614: Watch: fix crash when reloading files (@outsideris)

:book: Documentation

• #4630: Add options.require to Mocha constructor for root hook plugins on parallel runs (@juergba)
• #4617: Dynamically generating tests with top-level await and ESM test files (@juergba)
• #4608: Update default file extensions (@outsideris)

Also thanks to @outsideris for various improvements on our GH actions workflows.

8.3.2 / 2021-03-12

:bug: Fixes

• #4599: Fix regression in require interface (@alexander-fenster)

:book: Documentation

• #4601: Add build to GH actions run (@christian-bromann)
• #4596: Filter active sponsors/backers (@juergba)
• #4225: Update config file examples (@pkuczynski)

8.3.1 / 2021-03-06

:bug: Fixes

• #4577: Browser: fix EvalError caused by regenerator-runtime (@snoack)
• #4574: ESM: allow import from mocha in parallel mode (@nicojs)

8.3.0 / 2021-02-11

:tada: Enhancements

• #4506: Add error code for test timeout errors (@boneskull)
• #4112: Add BigInt support to stringify util function (@JosejeSinohui)

:bug: Fixes

• #4557: Add file location when SyntaxError happens in ESM (@giltayar)
• #4521: Fix require error when bundling Mocha with Webpack (@devhazem)

:book: Documentation

• #4507: Add support for typescript-style docstrings (@boneskull)
• #4503: Add GH Actions workflow status badge (@outsideris)
• #4494: Add example of generating tests dynamically with a closure (@maxwellgerber)

:nut_and_bolt: Other

• #4556: Upgrade all dependencies to latest stable (@AviVahl)
• #4543: Update dependencies yargs and yargs-parser (@juergba)

Also thanks to @outsideris and @HyunSangHan for various fixes to our website and documentation.

8.2.1 / 2020-11-02

Fixed stuff.

:bug: Fixes

• #4489: Fix problematic handling of otherwise-unhandled Promise rejections and erroneous "done() called twice" errors (@boneskull)
• #4496: Avoid MaxListenersExceededWarning in watch mode (@boneskull)

Also thanks to @akeating for a documentation fix!

8.2.0 / 2020-10-16

The major feature added in v8.2.0 is addition of support for global fixtures.

While Mocha has always had the ability to run setup and teardown via a hook (e.g., a before() at the top level of a test file) when running tests in serial, Mocha v8.0.0 added support for parallel runs. Parallel runs are incompatible with this strategy; e.g., a top-level before() would only run for the file in which it was defined.

With global fixtures, Mocha can now perform user-defined setup and teardown regardless of mode, and these fixtures are guaranteed to run once and only once. This holds for parallel mode, serial mode, and even "watch" mode (the teardown will run once you hit Ctrl-C, just before Mocha finally exits). Tasks such as starting and stopping servers are well-suited to global fixtures, but not sharing resources--global fixtures do not share context with your test files (but they do share context with each other).

Here's a short example of usage:

// fixtures.js

// can be async or not
exports.mochaGlobalSetup = async function () {
  this.server = await startSomeServer({port: process.env.TEST_PORT});
  console.log(`server running on port ${this.server.port}`);
};

exports.mochaGlobalTeardown = async function () {
  // the context (`this`) is shared, but not with the test files
  await this.server.stop();
  console.log(`server on port ${this.server.port} stopped`);
};

// this file can contain root hook plugins as well!
// exports.mochaHooks = { ... }

Fixtures are loaded with --require, e.g., mocha --require fixtures.js.

For detailed information, please see the documentation and this handy-dandy flowchart to help understand the differences between hooks, root hook plugins, and global fixtures (and when you should use each).

:tada: Enhancements

• #4308: Support run-once global setup & teardown fixtures (@boneskull)
• #4442: Multi-part extensions (e.g., test.js) now usable with --extension option (@jordanstephens)
• #4472: Leading dots (e.g., .js, .test.js) now usable with --extension option (@boneskull)
• #4434: Output of json reporter now contains speed ("fast"/"medium"/"slow") property (@wwhurin)
• #4464: Errors thrown by serializer in parallel mode now have error codes (@evaline-ju)

For implementors of custom reporters:

• #4409: Parallel mode and custom reporter improvements (@boneskull):
  • Support custom worker-process-only reporters (Runner.prototype.workerReporter()); reporters should subclass ParallelBufferedReporter in mocha/lib/nodejs/reporters/parallel-buffered
  • Allow opt-in of object reference matching for "sufficiently advanced" custom reporters (Runner.prototype.linkPartialObjects()); use if strict object equality is needed when consuming Runner event data
  • Enable detection of parallel mode (Runner.prototype.isParallelMode())

:bug: Fixes

• #4476: Workaround for profoundly bizarre issue affecting npm v6.x causing some of Mocha's deps to be installed when mocha is present in a package's devDependencies and npm install --production is run the package's working copy (@boneskull)
• #4465: Worker processes guaranteed (as opposed to "very likely") to exit before Mocha does; fixes a problem when using nyc with Mocha in parallel mode (@boneskull)
• #4419: Restore lookupFiles() in mocha/lib/utils, which was broken/missing in Mocha v8.1.0; it now prints a deprecation warning (use const {lookupFiles} = require('mocha/lib/cli') instead) (@boneskull)

Thanks to @AviVahl, @donghoon-song, @ValeriaVG, @znarf, @sujin-park, and @majecty for other helpful contributions!

8.1.3 / 2020-08-28

:bug: Fixes

• #4425: Restore Mocha.utils.lookupFiles() and Webpack compatibility (both broken since v8.1.0); Mocha.utils.lookupFiles() is now deprecated and will be removed in the next major revision of Mocha; use require('mocha/lib/cli').lookupFiles instead (@boneskull)

8.1.2 / 2020-08-25

:bug: Fixes

• #4418: Fix command-line flag incompatibility in forthcoming Node.js v14.9.0 (@boneskull)
• #4401: Fix missing global variable in browser (@irrationnelle)

:lock: Security Fixes

• #4396: Update many dependencies (@GChuf)

:book: Documentation

• Various fixes by @sujin-park, @wwhurin & @Donghoon759

8.1.1 / 2020-08-04

:bug: Fixes

• #4394: Fix regression wherein certain reporters did not correctly detect terminal width (@boneskull)