Angular on Bun (bun:test)

Angular has no bun test integration of its own. Two things are missing, and both are fatal on their own:

1. No DOM. Bun ships none, and everything from platformBrowserTesting() onwards reads document.
2. No template resolution. @Component({ templateUrl: './x.html' }) is not an import — nothing in the module graph points at the HTML file — so Angular's JIT compiler refuses to build the component ("Component X is not resolved"). Under Vitest, @analogjs/vite-plugin-angular inlines it during transform. Bun has no such transform.

vitest-auto-spy/bun-angular closes both, plus the wiring around them, from a single preload.

Setup

# bunfig.toml
[test]
preload = ["vitest-auto-spy/bun-angular"]

bun add -d @happy-dom/global-registrator   # or: bun add -d jsdom

That is the whole configuration. On load the entry:

1. installs a DOM — @happy-dom/global-registrator if present, otherwise jsdom, and nothing at all if a DOM is already there;
2. registers a Bun.plugin onLoad hook that inlines templateUrl / styleUrl / styleUrls into the component source;
3. initialises a zoneless TestBed environment and resets the testing module after each test;
4. registers the Bun mock adapter, so every spy helper is Bun's.

It has to be a preload

A Bun.plugin hook only sees modules loaded after it is registered. Importing this entry from inside a spec is too late for the component under test — its template will not be inlined. Importing it from a spec as well is fine: the module is cached and every step is guarded.

Writing a spec

From here a spec reads exactly like its Vitest counterpart.

// greeting.test.ts
import { TestBed } from '@angular/core/testing';
import { describe, expect, it } from 'bun:test';

import { GreetingComponent } from './greeting.component'; // declared with templateUrl
import { GreetingService } from './greeting.service';
import { injectSpy, provideAutoSpy, stable } from 'vitest-auto-spy/bun-angular';

describe('GreetingComponent', () => {
  it('renders the name the service returns', async () => {
    TestBed.configureTestingModule({ providers: [provideAutoSpy(GreetingService)] });

    injectSpy(GreetingService).currentName.mockReturnValue('external user');

    const fixture = TestBed.createComponent(GreetingComponent);

    await stable(fixture);

    expect(fixture.nativeElement.textContent).toContain('Hello, external user!');
  });
});

bun test              # add --isolate for a fresh global per file

What you get

Helper	Works on Bun	Notes
provideAutoSpy / injectSpy	✅	identical to the Vitest entry, lazy spies by default
renderShallow	✅	real ComponentFixture, child subtree dropped
createWithAutoSpies	✅	builds a class through Angular DI with every dep spied
stable / flushEffects	✅	zoneless waiting
the whole core (createSpyFromClass, …)	✅	re-exported from this entry
registerSignalMatchers	❌	needs the runner's expect.extend — Vitest only
TestBed diagnostics (instrumentTestBed)	❌	needs suite-level runner hooks — Vitest only

Stylesheets

A test runner has no CSS pre-processor, and no spec asserts on styles. So .css is inlined verbatim and everything else (.scss, .less, .styl) becomes an empty stylesheet — the component still compiles and renders. Override it if you genuinely need the text:

inlineAngularResources(source, path, { inlineStyleExtensions: ['.css', '.scss'] });

Building your own preload

Every piece is exported, so a project with its own preload can compose them instead of taking the defaults:

// bun-preload.ts
import { createJsdomRegistrar, inlineAngularResources, registerDomGlobals } from 'vitest-auto-spy/bun-angular';

await registerDomGlobals({
  registrars: [createJsdomRegistrar({ load: () => import('jsdom'), target: globalThis, url: 'https://app.test/' })],
});

registerDomGlobals returns the name of the registrar that installed the DOM, or undefined when one was already present, and throws with every attempt listed when none worked.

Limits worth knowing

• The rewrite is textual, not a parse. It skips comments and string literals — a templateUrl written in prose is left alone — but it does not track ${…} interpolation or regex literals.
• Line numbers are preserved. Every inlined value is a single-line literal, so a failing spec's stack trace still points at the component's own line.
• node_modules is skipped. Published Angular libraries are already compiled.
• This entry is ESM-only. It awaits its DOM registrar at the top level, which has no CommonJS form. Bun runs ESM natively, so nothing is lost.