Jest

The Jest module runs Jest tests for JavaScript and TypeScript projects as a Dagger check, locally, in CI, and in Dagger Cloud. Each Jest config roots a project, and each project's test files are a collection, so a check can run one project, one test file, or everything.

Add it to your workspace

dagger module install dagger.io/js/jest

Run the tests

dagger check --jest                                         # run every Jest project
dagger check --jest-project=apps/api                        # run one project
dagger check --jest-project=apps/api --jest-test-file=src/sub.test.js   # run one test file

The check is jest/projects/tests/test. It installs dependencies and runs the project's own Jest once per project, over the selected test files. With every file in the project selected, it runs jest with the project's config. With some selected, it runs only those files.

The module registers an OpenTelemetry hook, so individual tests appear as spans in the Dagger TUI and Dagger Cloud without changing the project's Jest config.

Collections

Flag	Collection	Key
--jest-project	projects	Directory holding the Jest config, relative to the workspace root. The root is .
--jest-test-file	tests, on a project	Test file path, relative to the project

List the keys with dagger list jest-projects -a and dagger list jest-test-files -a. Select collection items describes how to select items.

A project is a directory holding jest.config.js, .mjs, .cjs, .ts, .mts, .cts, or .json. Projects are found at or below the directory dagger runs from, plus the nearest project that encloses it. When a root config lists other projects in its projects field, those projects are tested through the root project and are not keys of their own.

Test files are found by reading the config's testMatch, testRegex, testPathIgnorePatterns, roots, and rootDir when they are literal values, and Jest's defaults otherwise. node_modules, .git, and files ignored by .gitignore are left out. A project with no test files has nothing to run.

Dependencies install at the nearest workspace root (a pnpm-workspace.yaml or a package.json with workspaces), else the nearest lockfile, else the nearest package.json.

To print the tests Jest discovers in a project, call its list function:

dagger -c 'jest | projects | get apps/api | list'

Configure it

List the current settings and their values with dagger module settings jest, then set one with dagger module settings jest <key> <value>. Settings are stored in dagger.toml under [modules.jest.settings] and apply to every project:

• packageManager (default empty) is the package manager that installs dependencies: npm, pnpm, yarn, or bun. Empty detects it from the packageManager field of package.json, then from the lockfile, then uses npm.
• baseImageAddress (default node:25-alpine) is the Node base image tests run in. Pin it to the project's Node version, for example node:22-alpine.
• build (default false) runs the package's build script before testing.
• useEnv (default false) uses the project's own Jest environment instead of injecting the module's OpenTelemetry hook.
• flags (default empty) are extra flags passed to every jest run.
• installFlags (default empty) are extra flags for the install command, such as ["--ignore-scripts"].
• environment (default empty) sets environment variables for the build and test steps, as KEY=VALUE.

[modules.jest.settings]
baseImageAddress = "node:22-alpine"
build = true
flags = ["--ci"]

Working with other modules

Use this module when Jest is the test runner. Use Vitest instead for projects built around Vitest or Vite-first test workflows.

source code