Interact with Workers

Use the test harness to send requests through configured routes or target a specific Worker directly. You can also dispatch events like scheduled events.

Test route dispatch across Workers

When a test harness runs multiple Workers, add each Worker to the workers array. The first Worker is the primary Worker. server.fetch() sends relative URLs to the primary Worker and matches absolute URLs against configured routes. If no route matches, it falls back to the primary Worker:

const server = createTestHarness({
	workers: [
		/** Includes `"routes": ["example.com/*"]` */
		{ configPath: "./workers/web/wrangler.jsonc" },
		/** Includes `"routes": ["api.example.com/v1/*"]` */
		{ configPath: "./workers/api/wrangler.jsonc" },
	],
});

const primaryResponse = await server.fetch("/");
const apiResponse = await server.fetch("http://api.example.com/v1/users/123");
const webResponse = await server.fetch("http://example.com/users/123");

const server = createTestHarness({
	workers: [
		/** Includes `"routes": ["example.com/*"]` */
		{ configPath: "./workers/web/wrangler.jsonc" },
		/** Includes `"routes": ["api.example.com/v1/*"]` */
		{ configPath: "./workers/api/wrangler.jsonc" },
	],
});

const primaryResponse = await server.fetch("/");
const apiResponse = await server.fetch("http://api.example.com/v1/users/123");
const webResponse = await server.fetch("http://example.com/users/123");

Interact with a specific Worker

Route dispatch tests the application boundary, but some tests might want to target one Worker or trigger other event handlers. Use server.getWorker(name) to bypass route matching and get a handle for that Worker.

You can then use this Worker handle to send requests directly or dispatch other events, such as scheduled():

const apiWorker = server.getWorker("api-worker");
const response = await apiWorker.fetch("http://api.example.com/v1/users/123");

await apiWorker.scheduled({
	cron: "0 0 * * *",
	scheduledTime: new Date(),
});

const apiWorker = server.getWorker("api-worker");
const response = await apiWorker.fetch("http://api.example.com/v1/users/123");

await apiWorker.scheduled({
	cron: "0 0 * * *",
	scheduledTime: new Date(),
});

Assert logged behavior

The test harness captures logs from the Workers runtime. To assert that a Worker logged a specific message, use server.getLogs() to retrieve the log entries.

Captured logs are reset when you call server.reset(). You can also call server.clearLogs() to isolate logs before and after a specific action:

test("logs scheduled job results", async ({ expect }) => {
	const apiWorker = server.getWorker("api-worker");

	await apiWorker.scheduled({
		cron: "0 0 * * *",
		scheduledTime: new Date("2026-05-29T00:00:00.000Z"),
	});

	expect(server.getLogs()).toEqual([
		expect.objectContaining({
			level: "info",
			message: "Generated daily report for 2026-05-29",
		}),
	]);

	server.clearLogs();

	await apiWorker.scheduled({
		cron: "0 0 * * *",
		scheduledTime: new Date("2026-05-30T00:00:00.000Z"),
	});

	expect(server.getLogs()).toEqual([
		expect.objectContaining({
			level: "info",
			message: "Generated daily report for 2026-05-30",
		}),
	]);
});

test("logs scheduled job results", async ({ expect }) => {
	const apiWorker = server.getWorker("api-worker");

	await apiWorker.scheduled({
		cron: "0 0 * * *",
		scheduledTime: new Date("2026-05-29T00:00:00.000Z"),
	});

	expect(server.getLogs()).toEqual([
		expect.objectContaining({
			level: "info",
			message: "Generated daily report for 2026-05-29",
		}),
	]);

	server.clearLogs();

	await apiWorker.scheduled({
		cron: "0 0 * * *",
		scheduledTime: new Date("2026-05-30T00:00:00.000Z"),
	});

	expect(server.getLogs()).toEqual([
		expect.objectContaining({
			level: "info",
			message: "Generated daily report for 2026-05-30",
		}),
	]);
});

Inspect and control Workflow execution

If your Worker starts a Workflow, you can use worker.introspectWorkflow(bindingName) to control new instances and inspect their state.

const worker = server.getWorker("api-worker");
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");
expect(await instance.getOutput()).toEqual({ approved: true });

const worker = server.getWorker<ApiEnv>("api-worker");
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");
expect(await instance.getOutput()).toEqual({ approved: true });

If the test already knows the instance ID, you can also introspect that instance directly with worker.introspectWorkflowInstance(bindingName, instanceId).

const instance = await worker.introspectWorkflowInstance(
	"MY_WORKFLOW",
	"instance-id",
);

await instance.modify(async (modifier) => {
	await modifier.mockStepResult({ name: "load-user" }, { id: "123" });
});

await instance.waitForStatus("complete");

const instance = await worker.introspectWorkflowInstance(
	"MY_WORKFLOW",
	"instance-id",
);

await instance.modify(async (modifier) => {
	await modifier.mockStepResult({ name: "load-user" }, { id: "123" });
});

await instance.waitForStatus("complete");