Unit Testing

• Vitest
  • Example Tests
• Other Testing Frameworks

Vitest

WXT provides first class support for Vitest for unit testing:

// vitest.config.ts
import { defineConfig } from 'vitest/config';
import { WxtVitest } from 'wxt/testing';

export default defineConfig({
  plugins: [WxtVitest()],
});

This plugin does several things:

• Polyfills the extension API, browser, with an in-memory implementation using @webext-core/fake-browser
• Adds all vite config or plugins in wxt.config.ts
• Configures auto-imports (if enabled)
• Applies internal WXT vite plugins for things like bundling remote code
• Sets up global variables provided by WXT (import.meta.env.BROWSER, import.meta.env.MANIFEST_VERSION, import.meta.env.IS_CHROME, etc)
• Configures aliases (@/*, @@/*, etc) so imports can be resolved

Here are real projects with unit testing setup. Look at the code and tests to see how they're written.

• aklinker1/github-better-line-counts
• wxt-dev/examples's Vitest Example

Example Tests

This example demonstrates that you don't have to mock browser.storage (used by wxt/storage) in tests - @webext-core/fake-browser implements storage in-memory so it behaves like it would in a real extension!

import { describe, it, expect } from 'vitest';
import { fakeBrowser } from 'wxt/testing';

const accountStorage = storage.defineItem<Account>('local:account');

async function isLoggedIn(): Promise<Account> {
  const value = await accountStorage.getValue();
  return value != null;
}

describe('isLoggedIn', () => {
  beforeEach(() => {
    // See https://webext-core.aklinker1.io/fake-browser/reseting-state
    fakeBrowser.reset();
  });

  it('should return true when the account exists in storage', async () => {
    const account: Account = {
      username: '...',
      preferences: {
        // ...
      },
    };
    await accountStorage.setValue(account);

    expect(await isLoggedIn()).toBe(true);
  });

  it('should return false when the account does not exist in storage', async () => {
    await accountStorage.deleteValue();

    expect(await isLoggedIn()).toBe(false);
  });
});

Other Testing Frameworks

To use a different framework, you will likely have to disable auto-imports, setup import aliases, manually mock the extension APIs, and setup the test environment to support all of WXT's features that you use.

It is possible to do, but will require a bit more setup. Refer to Vitest's setup for an example of how to setup a test environment:

https://github.com/wxt-dev/wxt/blob/main/packages/wxt/src/testing/wxt-vitest-plugin.ts