Upgrade guide

Upgrading from 2.x to Japa 3

v3 is the newer version of Japa. It comes with a handful of breaking changes along with migration to ESM.

Before upgrading any other plugins, you must upgrade the @japa/runner to the latest major release.

npm i @japa/runner@latest

Upgrade any of the following plugins you are using in your project. All Japa plugins have zero breaking changes during this release.

# If using the assert plugin
npm i @japa/assert@latest
# If using the expect plugin
npm i @japa/expect@latest
# If using the expect-type plugin
npm i @japa/expect-type@latest
# If using the api-client plugin
npm i @japa/api-client@latest
# If using the browser-client plugin
npm i @japa/browser-client@latest
# If using the snapshot plugin
npm i @japa/snapshot@latest
# If using the file-system plugin
npm i @japa/file-system@latest

Finally, please remove the following packages from your project since they have been deprecated. Learn more.

npm uninstall\

Breaking changes

Following is the list of breaking changes when migrating to Japa v3.

ESM only

Japa now only works with ESM projects. If your projects are not using ES modules (including AdonisJS v5 apps), you should stick with Japa v2. Link to v2 docs

Changes to the processCliArgs method

The behavior of the processCliArgs method has been changed completely.

  • The method has been renamed from processCliArgs to processCLIArgs.
  • Earlier, this method was used to convert CLI arguments into a config object. However, with v3, this method returns undefined, and Japa internally mutates the config based on the parsed CLI arguments.

You must make the following changes to the Japa entry point file, i.e., bin/test.js.

import {
} from '@japa/runner'
// Rest of the config

Changes to the reporters property

The reporters property inside the configuration block has been converted from an Array to an Object. The new reporters object contains a list of registered reporters and a list of activated reporters.

After this change, you can register multiple reporters but only activate a few. Or activate them using the CLI flag --reporters when running the tests.

Following is the list of changes you must make to the Japa entry point file.

import { specReporter } from '@japa/spec-reporter'
import { spec } from '@japa/runner/reporters'
reporters: [specReporter()]
reporters: {
activated: ['spec'],
list: [spec()]

Also, Japa v3 registers all the first-party reporters by default. Therefore, you can remove the reporters property from the config block, and everything will work as expected.

* The spec reporter is registered by default hence there
* is not need to register it manually.
reporters: {
activated: ['spec'],
list: [spec()]

Changes to plugin function arguments

Earlier, a plugin function was used to receive multiple arguments, which have been consolidated into a single options object in Japa v3.

If you have created plugins for Japa, you must make the following changes.

In Japa v2
export function myCustomPlugin(
config: Required<Config>,
runner: Runner,
classes: {
Test: typeof Test,
TestContext: typeof TestContext,
Group: typeof Group
) {
// plugin implementation
In Japa v3
export function myCustomPlugin(
options: {
config: Required<Config>
cliArgs: CLIArgs
runner: Runner
emitter: Emitter
) {}

Also, we no longer pass the Test, TestContext, and Group classes to a plugin. You can import them directly from the @japa/runner/core module.

import { Test, TestContext, Group } from '@japa/runner/core'

Other breaking changes

  • All types are exported from the @japa/runner/types submodule.

  • The config.importer method now receives an instance of the URL class. Earlier, it used to be an absolute file path. Ideally, you can remove the importer implementation from your config file since it converts the file path to a URL.

  • Removed the --ignore-tags CLI flags. Instead, you can negate the tags using the tilde ~ symbol

  • Use tilde ~ symbol for negating tags. The character was ! earlier, but you had to escape ! inside a terminal, whereas ~ needs no escaping.

Package removed

We have moved a lot of stuff within the @japa/runner codebase; hence, the following packages have been removed during the v3 release. These packages are not compatible with @japa/runner@3.

  • @japa/spec-reporter : Uninstall the package and remove its usage from the config file. Japa registers the spec reporter by default.

  • @japa/dot-reporter: Uninstall the package and remove its usage from the config file. Japa registers the dot reporter by default.

  • @japa/run-failed-tests: The plugin has been removed. Instead, you must run failed tests using the new --failed flag.

  • @japa/base-reporter: The base reporter was used to create custom reporters by extending the BaseReporter class. This class has been moved within the Runner codebase, and you can import it as follows.

    import { BaseReporter } from '@japa/runner/core'
    export class MyReporter extends BaseReporter {}
  • @japa/synthetic-events : The package was used to emit fake events that can be used to create a custom reporter. You do not need this package anymore. Instead, use the runner factory to test reporters.

New features

  • Introduce the --failed flag to run tests that failed from the previous run. No config changes are needed for this. Just use the CLI flag.

  • Introduce the —-retries flag to define the number of times a test should be retried after failure. The flag applies to all the tests that do not set an explicit retries count.

  • Add ndjson reporter. It is created specially for our VSCode extension.

  • Introduce SummaryBuilder that reporters and plugins can access from the runner object. The summary builder allows registering functions that can return a key-value pair to display inside the test summary output.

    runner.summaryBuilder.use(() => {
    return [
    key: 'Node.js version',
    value: process.version
  • Add the test.throws method to write high-order assertions. Learn more

Handling uncaught errors differently

Earlier, Japa used to try and associate uncaughtExceptions with the test that might have triggered it. This behavior was tricky and usually produced many false positives.

Also, we collected all the uncaughtExceptions until the process exits and displayed their count inside the tests runner summary output.

In Japa v3, the above-defined behaviors have been removed with a simple implementation. Now, Japa listens for uncaughtExceptions and uncaughtRejections globally and reports them as they occur. They are not aggregated in the output summary.

This change has no impact on the way you write tests.

Better errors output

Inspired by Vitest, we now display red borders around individual errors with a paging counter. The border makes it easy to scan errors when you have a massive list of them. You can easily see where an error starts and ends.

Old output

New Output