AVA 4

[novemberborn]

We're celebrating the new year with the official AVA 4 release! 🎊

npm install -D ava

The cool new stuff 🆒

Worker threads 🧑‍💼

By default, test files are now run in worker threads! Huge thanks to @dnlup for landing this.

Test files should run a little quicker, since it's easier to spin up a worker thread than a child process. You can use --no-worker-threads on the command line, or workerThreads: false in your AVA configuration, to fall back to using child processes.

Shared workers are no longer experimental 🎊

Shared workers are no longer experimental. This is a powerful feature that loads a program in a worker thread in AVA's main process and then communicate with code running in the test workers. This enables your tests to better utilize shared resources during a test run, as well as providing opportunities to set up these resources before tests start (or clean them up after).

When you use watch mode, shared workers remain loaded across runs.

Improved test selection 🤳

AVA selects test files based on your package.json or ava.config.* configuration files. When used on the CLI you can then provide patterns to select a subset of these files.

You can now pass a folder and AVA will select the test files contained therein. Or you can provide a specific JavaScript file and AVA will run it even if it wasn’t selected by your configuration.

If AVA finds files based on the configuration, but none of those were selected to the CLI arguments, it now prints a warning.

Better monorepo support 🚝

AVA now looks for ava.config.* files in parent directories, until it finds a directory with a .git directory (or file). This lets you specify AVA configuration at the top of your monorepo and still run AVA from within each package.

New snapshot format 📸

@ninevra has worked tirelessly on landing a new snapshot format. It contains all information necessary to regenerate the report file. This allows for snapshots to be updated even if tests or assertions are skipped.

Previously failing test files run first 🏃

AVA now records which test files failed in the previous run. It then prioritizes testing these files when you run AVA again. Thanks @bunysae!

ESM support 🤾

AVA 4 comes with full ES module support. Both ESM and CJS entrypoints are provided so that you can use it no matter how you manage your project.

The ava.config.js file is now treated as CJS or ESM depending on module type configured in the package.json file. ava.config.mjs is now supported.

If you use JavaScript files with non-standard extensions you can configure AVA to import them.

Note that dependency tracking in watch mode does not yet work with ES modules.

Dedicated macro factory with type inference 🏭

test.macro() returns an object that can be used with test() and hooks. The t.context type is inherited from test. When used with TypeScript this gives much better type inference.

Like with AVA 3, regular functions that also have a title property that is a string-returning function are supported. However the type checking won’t be as good.

Source maps 🗺

AVA now uses the source map support that’s built in to Node.js itself. This should give better stack traces. However we’re not sure yet what happens if you load a program that automatically modifies stack traces.

Line number selection (where npx ava test.js:5 runs the test at line 5) now uses source maps and so should work better with TypeScript files.

Assertions as type guards 💂

Most assertions now return a boolean indicating whether they passed. If you use AVA with TypeScript, you can use this as a type guard. Thanks @jmarkham828!

(This is not supported for t.snapshot() and the "throws" assertions.)

Breaking changes 💥

AVA 4 requires at least Node.js 12.22, 14.17, 16.4 or 17. Node.js 10 is no longer supported.

If installed globally, AVA will no longer use any locally installed version. Install locally and run with npx ava instead. When running test files from another project that also has AVA installed, those test files will now fail to run (because they'll try and use that other AVA version).

Ecosystem 🏞

• Support for @ava/babel has been removed. We haven’t seen enough contributions to that package to recommend it for AVA 4. We’d be open to reinstating it in the future (just as we’d be open to support any other compilation provider).
• As a consequence, “enhanced assertions” are no longer available.
• AVA 4 requires avajs/typescript@1.1 or newer.
• Support for the esm package has been removed.

Configuration 🗒

• ava.config.js now follows the module type configured in package.json.
• ava.config.* files may be found that are outside your project directory.

Tests and assertions 🥼

• By default test files execute in worker threads, not child processes.
• test.meta.file and test.meta.snapshotDirectory are now file URL strings.
• Whitespace in test titles is now normalized. This could result in two tests being treated as having the same title, even though they are different in code. Thanks @KillyMXI!
• test() and t.try() no longer take an array of test implementations. Use a loop instead.
• The t.throws() and t.throwAsync() assertions can no longer be called with a null value for the expectations argument.
• test.cb() and t.end() have been removed. Use async functions and util.promisify() instead.
• t.teardown() now executes in last-in-first-out order.

Snapshots 📸

• Snapshots recorded using earlier AVA versions are no longer recognized. Run npx ava -u to rebuild your snapshots after upgrading.
• Snapshots no longer recognize React elements, instead we want to provide this functionality through a plugin interface
• t.snapshot() no longer works in hooks.
• t.snapshot() no longer takes an options argument allowing you to customize the snapshot ID.

TypeScript 🪛

• The instanceOf expectation of t.throws() and t.throwsAsync() assertions must now be an Error constructor.
• You’re expected to use test.macro() when declaring macros.
• Implementation arguments now default to unknown.
• Types have been renamed. Meta replaces MetaInterface, other types with Interface suffixes now use the Fn suffix. There may be some other changes too. 4b4b2f6
• t.throws() and t.throwsAsync() return undefined when the assertion fails. The type definition now matches this behavior.
• Our TypeScript definitions are now tested against TypeScript 4.4

Other changes 🤓

• We’ve removed the non-verbose reporter because it proved too hard to maintain two subtly different reporter outputs. We’d really like to rewrite the reporter.
• AVA's configuration files may now export promises or asynchronous factory methods.
• The --config argument may now point to a file that is not alongside the package.json file.
• When you use t.timeout(), AVA itself won’t time out until your test does. Thanks @OhYash!
• Multi-line snapshot labels now render correctly in Markdown. Thanks @KillyMXI!
• The reporters now clean up .test and .spec extensions from file names, as well as test- prefixes.
• Watch mode is better at detecting changes to snapshots and not rerunning tests.

New Contributors

• @Fem-Fem made their first contribution in Improve callsite handling #2750
• @OhYash made their first contribution in Have the global timeout take into account t.timeout() durations #2758
• @KillyMXI made their first contribution in Support multiline snapshot labels #2773
• @mcecode made their first contribution in Clarify caching #2794
• @duncanfinney made their first contribution in Match name of debug task to current VSCode #2820
• @asaid-0 made their first contribution in Normalize glob patterns with trailing slashes #2788
• @bompus made their first contribution in Use c8 for code coverage examples instead of nyc #2843
• @StefanoA1 made their first contribution in Fix typo in documentation #2849
• @live627 made their first contribution in Replace Lodash with built-in syntax, libraries, and some code #2851
• @alessandroasm made their first contribution in Remove dependency on read-pkg #2863
• @eltociear made their first contribution in Fix typo in assertions documentation #2870
• @hamidbae made their first contribution in Update Mongoose recipe #2878
• @rrichardson made their first contribution in Mention experimental specifier resolution in TypeScript recipe #2910
• @make-github-pseudonymous-again made their first contribution in Improve wording in TypeScript recipe #2913
• @lightmare made their first contribution in Remove dependency on equal-length #2918

Full changelog since RC 1: v4.0.0-rc.1...v4.0.0
Full changelog since AVA 3: v3.15.0...v4.0.0

---

This discussion was created from the release AVA 4.

[Brooooooklyn]

wokerThreads: true cause 0xc0000005 (Access Violation) on Windows. See https://github.com/napi-rs/napi-rs/runs/4697819504?check_suite_focus=true

Disabled workerThreads could fix it: napi-rs/napi-rs#1004

[novemberborn]

I think this is a limitation in Node-API or perhaps something your project needs to deal with. I suspect your code won't work in worker threads at all. This shouldn't be AVA specific.

[tommy-mitchell]

What was the reasoning behind the change to t.throws and t.throwsAsync to possibly return undefined?

[novemberborn]

That was just a type change to match the runtime behavior. The assertion returns undefined if it did not capture an error.

[tommy-mitchell]

Do tests not just end if it doesn’t throw?

[novemberborn]

AVA's assertions don't throw when they fail, so no the tests keep running.