Summary
On July 27, 2026, Cloudflare added createTestHarness() to Wrangler, an API for running integration tests across Workers. It supports multi-Worker routing, request mocking, and Playwright integration, letting developers exercise realistic cross-Worker request flows and browser-driven scenarios in automated tests rather than only unit-testing individual Workers.
What changed
Wrangler introduced createTestHarness() (changelog dated 2026-07-27), an integration-test API covering multi-Worker routing, request mocking, and Playwright integration.
Why it matters
As Workers apps grow into multi-Worker systems (service bindings, agents, MCP servers), unit tests alone miss routing and cross-service behavior. A first-party integration harness with browser support closes a real gap in the Workers testing story and makes it easier to ship agent and API backends on Cloudflare with confidence, reducing reliance on ad-hoc test scaffolding.
Evidence excerpt
Wrangler now provides createTestHarness(), an API for running integration tests that supports multi-worker routing, request mocking, and Playwright integration.