createTestHarness() introspects Workflow bindings
Introduced 2026-06-30 · score 0.98
HOW TO USE IT
When a Worker route starts a Workflow, use `createTestHarness()` to introspect its binding, disable the named sleep, trigger the route, and wait for the instance to complete.
const harness = createTestHarness({ workers: [{ configPath: "./wrangler.json" }] });
const worker = harness.getWorker();
await using workflow = await worker.introspectWorkflow("MY_WORKFLOW");
await workflow.modifyAll(async (modifier) => {
await modifier.disableSleeps([{ name: "wait-for-approval" }]);
});
await worker.fetch("/start-workflow");
const [instance] = await workflow.get();
await instance.waitForStatus("complete");WHY THIS HELPS
Test a Worker route that starts a Workflow and wait for the resulting Workflow instance to complete.
REQUIREMENTS AND LIMITATIONS
- Version: wrangler@4.106.0
- workers[].configPath (required): Path to the Worker Wrangler configuration file.
- bindingName (required): Workflow binding name to introspect; instances created after introspection starts are captured.
- disableSleeps([{ name }]): Disables the specified Workflow sleep; `name` identifies the sleep step.
- waitForStatus(status) (required): Waits until the instance reaches the requested status; use `"complete"` here.
- Prerequisite: A Worker project with a Wrangler configuration file, a Node.js test runner, and `wrangler` installed as a development dependency.
- Introspection is by Workflow binding name.
- Tests can introspect a known Workflow instance by ID or track instances created after introspection starts.
- Docs conflict: Current documentation was last updated July 27, 2026, after Wrangler 4.106.0. Its example uses an async `modifyAll` callback and awaits `disableSleeps`; the release-note example uses a synchronous callback. The release note is retained for the target version.
FIRST-PARTY EVIDENCE
- https://github.com/cloudflare/workers-sdk/releases/tag/wrangler%404.106.0
- https://developers.cloudflare.com/workers/testing/test-harness/interact-with-workers/
- https://developers.cloudflare.com/workers/testing/test-harness/get-started/
Check the installed version and the source before using it. Entry JSON