Vitest preset

Installation

Add a single entry to vitest.config.ts:

import { defineConfig } from 'vitest/config';

export default defineConfig({
  test: {
    setupFiles: ['extforge/testing/vitest'],
  },
});

No other setup is required.

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What it does

On first import, the preset:

1. Calls installChromeFakes() — mounts fake chrome.* namespaces on globalThis.chrome. Each namespace is wrapped in a Proxy so accessing an unmodeled method throws immediately with a descriptive error.
2. Registers a beforeEach hook — calls resetChromeFakes(fakes) before every test to clear storage state, listener arrays, and spy call counts.
3. Exports the fakes bag — so test files can fire events and inspect state.

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The fakes export

import { fakes } from 'extforge/testing/vitest';

fakes is a ChromeFakes object:

interface ChromeFakes {
  runtime:   RuntimeFake;   // fakes.runtime.fireOnMessage(...)
  storage:   StorageFake;   // fakes.storage.chrome.local.__state()
  tabs:      TabsFake;      // fakes.tabs.__seed([...])
  action:    ActionFake;    // fakes.action.reset()
  scripting: ScriptingFake; // fakes.scripting.__nextResult(value)
  reset():   void;          // called automatically by beforeEach
}

Each namespace’s fake is documented in chrome-fakes.

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When NOT to use the preset

Do not use the preset if:

• You already define globalThis.chrome in your test environment (the preset throws if chrome is already defined).
• You need fine-grained control over which fakes are installed per test suite. Use createChromeFakes() or the per-namespace factories (createRuntimeFake(), etc.) instead and install them manually.
• You are testing in a non-Vitest environment (e.g. Jest). The preset imports beforeEach from Vitest. For Jest, construct fakes manually and register beforeEach(() => fakes.reset()) yourself.