# Angular Testing

Ionic Framework supports multiple versions of Angular. As a result, we need to verify that Ionic works correctly with each of these Angular versions.

## Syncing Local Changes

The Angular test app supports syncing your locally built changes for validation. This allows you to test local changes like `core` without having to publish a new version of the package.

> [!TIP]
> In the root directory, run `npm unlink *` to remove any previous links you have built.

1. Build the `core` directory.
2. Navigate to `packages/angular` and run `npm run sync`.
3. Build `packages/angular` using `npm run build`.
4. Navigate to `packages/angular-server` and run `npm install && npm run build`.
5. [Build the Angular test app](#test-app-build-structure).
6. Navigate to the built test app directory (e.g. `packages/angular/test/build/ng14`).
7. Install dependencies using `npm install`.
8. Sync your local changes using `npm run sync`.

From here you can either build the application or start a local dev server. When re-syncing changes, you will need to [wipe or disable the application cache](#application-cache).

> [!NOTE]
> Syncing is required to verify that the minimal supported Angular version is still compatible with the latest Ionic Framework changes.
> For example, Ionic Framework 9 supports Angular 18, but the latest version of Ionic Framework may not be compatible with Angular 18. Syncing allows you to verify that the latest changes are still compatible with the minimal supported version.
>
> Support for the minimal version and maximum version can be found on the [Support page](https://ionicframework.com/docs/reference/support#ionic-angular) of the Ionic Framework documentation.

## Application Cache

Angular CLI creates a cache of several files on disk by default in the `.angular` directory. This decreases the time taken to build the test application. However, the cache makes it difficult to quickly sync and check local changes of Ionic. As a result, the `.angular` cache is disabled by default in the test app projects.

See https://angular.io/cli/cache for more information.

### Disable Cache

```shell
ng cache disable
```

> [!NOTE]
> You may need to manually remove the `.angular` directory once after running this command.

### Enable Cache

```shell
ng cache enable
```

> [!NOTE]
> You will need to delete the `.angular` cache and restart the dev server every time you want to sync local changes of Ionic.

## Test App Build Structure

> [!NOTE]
> Please confirm your current directory as `packages/angular/test` before proceeding with any of the following commands.

Unlike other test applications, these test apps are broken up into multiple directories. These directories are then combined to create a single application. This allows us to share common application code, tests, etc so that each app is being tested the same way. Below details the different pieces that help create a single test application.

**apps** - This directory contains partial applications for each version of Angular we want to test. Typically these directories contain new `package.json` files, `angular.json` files, and more. If you have code that is specific to a particular version of Angular, put it in this directory.

**base** - This directory contains the base application that each test app will use. This is where tests, application logic, and more live. If you have code that needs to be run on every test app, put it in this directory.

**build** - When the `apps` and `base` directories are merged, the final result is put in this directory. The `build` directory should never be committed to git.

**build.sh** - This is the script that merges the `apps` and `base` directories and places the built application in the `build` directory.

Usage:

```shell
# Build a test app using apps/ng14 as a reference
./build.sh ng14
```

## How to modify test apps

To add new tests, components, or pages, modify the `base` project. This ensures that tests are run for every tested version.

If you want to add a version-specific change, add the change inside of the appropriate projects in `apps`. Be sure to replicate the directory structure. For example, if you are adding a new E2E test file called `test.spec.ts` in `apps/ng14`, make sure you place the file in `apps/ng14/e2e/src/test.spec.ts`.

### Version-specific tests

If you need to add E2E tests that are only run on a specific version of the JS Framework, replicate the `VersionTest` component on each partial application. This ensures that tests for framework version X do not get run for framework version Y.

### Testing Lazy Loaded Ionic Components

Tests for lazy loaded Ionic UI components should only be added under the `/lazy` route. This ensures the `IonicModule` is added.

> [!CAUTION]
> The lazy loaded build, including `IonicModule`, is deprecated and will be removed in a future major version. New components should be tested as standalone components (see below). These lazy tests remain to verify that the deprecated build keeps working while it is still supported.

### Testing Standalone Ionic Components

Tests for standalone Ionic UI components should only be added under the `/standalone` route. This allows for an isolated environment where the lazy loaded `IonicModule` is not initialized. The standalone components use Stencil's custom element bundle instead of the lazy loaded bundle. If `IonicModule` is initialized then the Stencil components will fall back to using the lazy loaded implementation instead of the custom elements bundle implementation.

### Waiting for Ionic Components

Use the `componentOnReady` helper exported from `@ionic/core` rather than calling `el.componentOnReady()` directly. That method only exists on lazy loaded elements, so a direct call throws under the `/standalone` route. The helper covers both: under `/lazy` it awaits the element's own `componentOnReady()` promise, and under `/standalone` it waits one animation frame, giving the component's inner contents a chance to render.

## Adding New Test Apps

As we add support for new versions of Angular, we will also need to update this directory to test against new applications. The following steps can serve as a guide for adding new apps:

1. Navigate to the built app for the most recent version of Angular that Ionic tests.
2. Update the application by following the steps on https://update.angular.io/.
3. Make note of any files that changed during the upgrade (`package.json`, `package-lock.json`, `angular.json`, etc).
4. Copy the changed files to a new directory in `apps`.
  - Do NOT copy the entire directory. The `test/base` directory contains shared files between all major versions. Only files that are different than previous major versions should be copied to the new directory in `apps`.
5. Add the new app to the `apps` matrix of the `test-angular-e2e` job in both `./github/workflows/build.yml` and `./github/workflows/stencil-nightly.yml`. This will allow the new test app to run against all PRs.
6. Commit these changes and push.

Example:

In this example, we are going to add the Angular 14 test app.

1. Build the Angular 13 test app using `./build.sh ng13`.
2. Navigate to `build/ng13`.
3. Perform the upgrade steps on https://update.angular.io/. The "From" field should say "13.0" and the "To" field should say "14.0".

Note: You may encounter some other peer dependency issues not covered by the Angular Upgrade Guide. These peer dependency issues can be resolved manually by updating the installed version of each dependency.

4. Observe that the output of the Angular upgrade indicates that the following files were modified:

`angular.json`
`package-lock.json`
`package.json`
`tsconfig.json`
`src/app/form/form.component.ts`
`src/app/modal-example/modal-example.component.ts`

5. Create a directory in `apps` named `ng14`.
6. Copy the modified files to the `apps/ng14` directory.
7. Open `./github/workflows/build.yml` and find the `test-angular-e2e` job.
8. Find the `apps` field under `matrix`.
9. Add "ng14" to the `apps` field.
10. Open `./github/workflows/stencil-nightly.yml` and find the `test-angular-e2e` job.
11. Repeat steps 8 and 9.
12. Commit these changes and push.

## Variant Test Apps

Most apps in `apps/` pin a different Angular version. A variant app pins the same version as an existing app and changes how it's configured, covering a combination that would otherwise go untested. The current example is `ng22-zone`: Angular 22 with Zone.js, the combination whose absence let [#31406](https://github.com/ionic-team/ionic-framework/issues/31406) ship.

Follow the steps above for adding a version app, with two differences:

1. **Name it `ng<NN>-<variant>`.** The Vercel preview app is picked in `core/scripts/vercel-build.sh` with the filter `'^ng[0-9]+$'`, so any suffixed name is excluded. A bare `ng<NN>` name is the trap: calling an Angular 22 variant `ng23` would match the filter and silently become the deployed preview.
2. **Select change detection through providers, not polyfills.** Angular 22 bootstraps zoneless even when Zone.js is loaded, so the mode is chosen by `base/src/app/change-detection.providers.ts`, which both `app.module.ts` and `main-standalone.ts` spread. Override that file in the variant app. It's empty in `base/`, which leaves Angular's own default. Omit `src/polyfills.ts` if the variant needs base's `import 'zone.js'`.

Shared pages under `base/` must keep passing in every mode, so use the `assertZoneContext()` helper from `base/src/app/zone-assert.util.ts` rather than asserting an Angular zone unconditionally.

For the change detection rules that apply to the library itself, see [Change Detection](./change-detection.md).