cloudflare--workers-sdk/fixtures/create-test-harness-example/README.md

Integration testing Workers with createTestHarness()

This fixture is the complete runnable example linked from the createTestHarness() docs. It shows how to test a realistic multi-Worker app's production build output from different test runners.

For the testing patterns demonstrated here, refer to the createTestHarness() examples guide.

Example app

The app has three Workers:

Worker	Route	Role
web-worker	example.com/*	Handles user-facing routes, calls the API Worker over a service binding, and uses Browser Rendering to generate previews.
api-worker	api.example.com/v1/*	Fetches upstream user data, caches it in KV, and stores scheduled reports in D1.
mock-browser	none	Test-only Worker used to replace the Web Worker's Browser Rendering binding.

What this fixture covers

• Setup Vitest against Workers developed with Wrangler.
• Setup Playwright against Workers built by the Cloudflare Vite plugin.
• Route dispatch across multiple Workers.
• Direct Worker calls with server.getWorker(name).
• D1 migration setup with worker.applyD1Migrations().
• Scheduled handler dispatch.
• Test-only binding overrides for platform bindings.
• Calling a Worker's default export with server.getWorker(name).getExport().
• Outbound request mocking with MSW.
• Local storage reset between tests.
• Debug output with server.debug().
• Runtime log assertions with server.getLogs() and server.clearLogs().

Run this example

To build the packages, run:

pnpm build --filter @fixture/create-test-harness-example

Then run the tests with:

pnpm --filter @fixture/create-test-harness-example test:vitest
pnpm --filter @fixture/create-test-harness-example test:playwright

Files

File	Purpose
tests/vitest.test.ts	Example for testing with Vitest.
tests/playwright.test.ts	Example for testing with Playwright.
vite.config.ts	Builds Vite-generated Worker configs.
workers/web/index.ts	User-facing Worker with service and Browser Rendering binding logic.
workers/web/wrangler.jsonc	Web Worker config.
workers/web/worker-configuration.d.ts	Generated Web Worker types.
workers/api/index.ts	API Worker with KV, D1, and scheduled job logic.
workers/api/wrangler.jsonc	API Worker config.
workers/api/worker-configuration.d.ts	Generated API Worker types.
workers/mock-browser/index.ts	Test-only mock Worker for the Browser Rendering binding.
workers/mock-browser/wrangler.jsonc	Mock Browser Worker config.

Related docs

• createTestHarness() guide
• createTestHarness() API reference