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This runs Jest on the outputs of the built test files and reports the results of the test execution. It depends on `jest` and `jest-environment-jsdom` as optional peer deps validated in the builder, so there isn't a strict dependency on Jest for applications which don't use it.
Jest exports a `runJest()` function, however it can't be used directly because we need to opt-in to `--experimental-vm-modules` in ordre to run Jest on native ESM JavaScript as produced by `browser-esbuild`. This means we need a Node subprocess in order to add this flag, because the `ng` command cannot add a Node flag to its own current execution. This unfortunately means we can't just `import * as jest from 'jest';` or even `require.resolve('jest')` because that returns the library entry point exporting `runJest()`, rather than a script which actually runs Jest on load. Fortunately, Jest exports it's `node_modules/.bin/jest` entry point from its `package.json` under `jest/bin/jest`, so we `require.resolve()` _that_ to get the path to the correct file.
Executing Jest is fairly straightforward, running on the output of the `browser-esbuild` execution with outputs streamed to the console. We opted to use JSDom over Domino in order to align with the existing Jest ecosystem.
@angular-devkit/build-angular
This package contains Architect builders used to build and test Angular applications and libraries.
Builders
| Name | Description |
|---|---|
| app-shell | Build an Angular App shell. |
| browser | Build an Angular application targeting a browser environment. |
| dev-server | A development server that provides live reloading. |
| extract-i18n | Extract i18n messages from an Angular application. |
| karma | Execute unit tests using Karma test runner. |
| ng-packagr | Build and package an Angular library in Angular Package Format (APF) format using ng-packagr. |
| server | Build an Angular application targeting a Node.js environment. |
| protractor | Deprecated - Run end-to-end tests using Protractor framework. |
Disclaimer
While the builders when executed via the Angular CLI and their associated options are considered stable, the programmatic APIs are not considered officially supported and are not subject to the breaking change guarantees of SemVer.