Workers Integration Testing

Workers Integration Testing

You write integration tests that exercise Cloudflare Workers through the real Workers runtime — not mocks. Every route, middleware chain, binding interaction, and error path is tested via SELF.fetch() against the actual handler with real (local) bindings. This is the highest-value testing layer for Workers because it catches what unit tests cannot: binding misconfigurations, middleware ordering bugs, serialization mismatches, and D1/KV/R2 query errors.

When to use this skill

• A new API route or endpoint is added to a Worker
• Middleware (auth, CORS, validation) is changed
• Database schema or queries change (D1, Hyperdrive/Postgres)
• KV, R2, or Durable Object interactions are added or modified
• As the primary test strategy in /nightshift, /swarm, and /ralph-tdd loops when the target is a Cloudflare Worker

Core principles

1. Test the HTTP seam. Use SELF.fetch() to call your Worker exactly as a client would. Assert on HTTP status, response body shape, and headers — not internal function return values.
2. Verify side effects in bindings. After a mutation endpoint (POST, PUT, DELETE), query the binding directly (env.DB.prepare(...), env.KV.get(...)) to confirm the write landed correctly.
3. No mocking bindings. The @cloudflare/vitest-pool-workers pool gives you real local bindings via Miniflare. Use them. Mock only truly external third-party services (payment gateways, external APIs).
4. Isolated storage per test. Use isolatedStorage: true so each test starts clean. Seed only what the test needs in beforeEach.
5. Test auth paths. Every protected endpoint needs at least: valid auth → 200, missing auth → 401, invalid auth → 401/403.
6. Test validation paths. Every endpoint that accepts a body needs: valid body → success, missing required fields → 400, invalid values → 400.

Setup

1. Install dependencies

pnpm add -D @cloudflare/vitest-pool-workers vitest

2. Vitest config

Create vitest.integration.config.mts (or add to existing vitest.config.ts):

import { defineWorkersConfig } from "@cloudflare/vitest-pool-workers/config";

export default defineWorkersConfig({
  test: {
    globals: true,
    include: ["test/integration/**/*.test.ts"],
    setupFiles: ["./test/integration/setup.ts"],
    poolOptions: {
      workers: {
        wrangler: {
          configPath: "./wrangler.toml", // or wrangler.jsonc
        },
        miniflare: {
          bindings: {
            // Override secrets for tests
            JWT_SECRET: "test-jwt-secret",
          },
          // For Hyperdrive (Postgres):
          // hyperdrives: { HYPERDRIVE: `${connectionString}/postgres` },
        },
        isolatedStorage: true,
        singleWorker: true,
      },
    },
  },
});

3. Setup file (D1 example)

// test/integration/setup.ts
import { env } from "cloudflare:test";

const schema = `
CREATE TABLE IF NOT EXISTS users (
  id TEXT PRIMARY KEY,
  email TEXT NOT NULL UNIQUE,
  created_at TEXT NOT NULL DEFAULT (datetime('now'))
);
`;

const statements = schema.split(";").map(s => s.trim()).filter(s => s.length > 0);
for (const stmt of statements) {
  await env.DB.prepare(stmt).run();
}

// Seed baseline data
await env.DB.prepare(
  "INSERT OR IGNORE INTO api_keys (key, name) VALUES (?, ?)"
).bind("test-api-key", "Test Key").run();

4. Package script

{
  "scripts": {
    "test:integration": "vitest run --config vitest.integration.config.mts"
  }
}

Test patterns

Full HTTP cycle with binding verification

import { env, SELF } from "cloudflare:test";
import { describe, it, expect, beforeEach } from "vitest";

describe("POST /api/v1/items", () => {
  beforeEach(async () => {
    await env.DB.prepare("DELETE FROM items").run();
  });

  it("creates item and persists to D1", async () => {
    const res = await SELF.fetch("https://api.test/api/v1/items", {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        Authorization: "Bearer test-api-key",
      },
      body: JSON.stringify({ name: "Widget", quantity: 5 }),
    });

    expect(res.status).toBe(201);
    const body = (await res.json()) as { id: string; name: string };
    expect(body.name).toBe("Widget");

    // Verify in D1
    const row = await env.DB.prepare(
      "SELECT * FROM items WHERE id = ?"
    ).bind(body.id).first();

    expect(row).toBeTruthy();
    expect(row!.name).toBe("Widget");
    expect(row!.quantity).toBe(5);
  });
});

Auth boundary tests

it("rejects missing auth", async () => {
  const res = await SELF.fetch("https://api.test/api/v1/items", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ name: "Widget" }),
  });
  expect(res.status).toBe(401);
});

it("rejects invalid key against real binding", async () => {
  const res = await SELF.fetch("https://api.test/api/v1/items", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: "Bearer not-a-real-key",
    },
    body: JSON.stringify({ name: "Widget" }),
  });
  expect(res.status).toBe(401);
  const body = (await res.json()) as { error: { code: string } };
  expect(body.error.code).toBe("invalid_api_key");
});

Validation boundary tests

it("rejects missing required fields", async () => {
  const res = await SELF.fetch("https://api.test/api/v1/items", {
    method: "POST",
    headers,
    body: JSON.stringify({ name: "Widget" }), // missing quantity
  });
  expect(res.status).toBe(400);
});

it("rejects invalid field values", async () => {
  const res = await SELF.fetch("https://api.test/api/v1/items", {
    method: "POST",
    headers,
    body: JSON.stringify({ name: "", quantity: -1 }),
  });
  expect(res.status).toBe(400);
});

CRUD lifecycle

it("full create → read → update → delete lifecycle", async () => {
  // Create
  const createRes = await SELF.fetch("https://api.test/api/v1/items", {
    method: "POST", headers,
    body: JSON.stringify({ name: "Widget", quantity: 5 }),
  });
  const { id } = (await createRes.json()) as { id: string };

  // Read
  const getRes = await SELF.fetch(`https://api.test/api/v1/items/${id}`, { headers });
  expect(getRes.status).toBe(200);

  // Update
  const putRes = await SELF.fetch(`https://api.test/api/v1/items/${id}`, {
    method: "PUT", headers,
    body: JSON.stringify({ quantity: 10 }),
  });
  expect(putRes.status).toBe(200);

  // Verify update in D1
  const row = await env.DB.prepare("SELECT quantity FROM items WHERE id = ?")
    .bind(id).first<{ quantity: number }>();
  expect(row?.quantity).toBe(10);

  // Delete
  const delRes = await SELF.fetch(`https://api.test/api/v1/items/${id}`, {
    method: "DELETE", headers,
  });
  expect(delRes.status).toBe(200);

  // Verify gone
  const gone = await env.DB.prepare("SELECT * FROM items WHERE id = ?")
    .bind(id).first();
  expect(gone).toBeNull();
});

KV binding tests

it("caches response in KV", async () => {
  const res = await SELF.fetch("https://api.test/api/v1/config", { headers });
  expect(res.status).toBe(200);

  const cached = await env.CONFIG_KV.get("config:latest");
  expect(cached).toBeTruthy();
});

Durable Object tests

import { env, SELF } from "cloudflare:test";

it("creates and retrieves DO state via HTTP", async () => {
  const res = await SELF.fetch("https://api.test/api/v1/rooms", {
    method: "POST", headers,
    body: JSON.stringify({ roomId: "room-1" }),
  });
  expect(res.status).toBe(201);

  // Interact with the room through the Worker's HTTP API
  const joinRes = await SELF.fetch("https://api.test/api/v1/rooms/room-1/join", {
    method: "POST", headers,
    body: JSON.stringify({ userId: "user-1" }),
  });
  expect(joinRes.status).toBe(200);
});

404 and error path tests

it("returns 404 for non-existent resource", async () => {
  const res = await SELF.fetch("https://api.test/api/v1/items/no-such-id", { headers });
  expect(res.status).toBe(404);
});

it("returns 405 for unsupported method", async () => {
  const res = await SELF.fetch("https://api.test/api/v1/items", {
    method: "PATCH", headers,
  });
  expect([404, 405]).toContain(res.status);
});

WebSocket / Durable Object tests

Workers that use Durable Objects with WebSocket hibernation need integration tests at both the HTTP upgrade seam and the message-handling seam.

WebSocket upgrade via Miniflare

When using @cloudflare/vitest-pool-workers or Miniflare directly, test the full upgrade handshake:

import { env, SELF } from "cloudflare:test";

it("upgrades to WebSocket and receives initial state", async () => {
  const res = await SELF.fetch("https://api.test/api/room/room-1", {
    headers: {
      Upgrade: "websocket",
      Connection: "Upgrade",
      Authorization: "Bearer test-token",
    },
  });

  expect(res.status).toBe(101);
  const ws = res.webSocket!;
  ws.accept();

  // Collect messages
  const messages: string[] = [];
  ws.addEventListener("message", (event: { data: unknown }) => {
    if (typeof event.data === "string") messages.push(event.data);
  });

  // Send an event to the DO
  ws.send(JSON.stringify({ type: "JOIN", userId: "user-1" }));

  // Give the DO time to process
  await new Promise((r) => setTimeout(r, 50));

  // Verify server sent state update
  expect(messages.length).toBeGreaterThan(0);
  const update = JSON.parse(messages[0]);
  expect(update).toHaveProperty("type");

  ws.close();
});

Testing multiple concurrent clients

it("broadcasts state changes to all connected clients", async () => {
  // Connect two clients
  const [ws1, ws2] = await Promise.all([
    connectWebSocket("room-1", "user-1"),
    connectWebSocket("room-1", "user-2"),
  ]);

  const ws2Messages: string[] = [];
  ws2.addEventListener("message", (e: { data: unknown }) => {
    if (typeof e.data === "string") ws2Messages.push(e.data);
  });

  // Client 1 sends action
  ws1.send(JSON.stringify({ type: "INCREMENT" }));
  await new Promise((r) => setTimeout(r, 50));

  // Client 2 should receive the state update
  expect(ws2Messages.length).toBeGreaterThan(0);

  ws1.close();
  ws2.close();
});

async function connectWebSocket(roomId: string, userId: string) {
  const res = await SELF.fetch(`https://api.test/api/room/${roomId}`, {
    headers: {
      Upgrade: "websocket",
      Connection: "Upgrade",
      Authorization: `Bearer token-${userId}`,
    },
  });
  expect(res.status).toBe(101);
  const ws = res.webSocket!;
  ws.accept();
  return ws;
}

FakeWebSocket for unit-testing DO handlers

When you need faster tests that skip the network layer and test DO logic directly:

class FakeWebSocket {
  sent: string[] = [];
  closeCalls: Array<{ code: number; reason: string }> = [];
  private attachment: unknown;

  send(payload: string) { this.sent.push(payload); }
  close(code: number, reason: string) { this.closeCalls.push({ code, reason }); }
  serializeAttachment(value: unknown) { this.attachment = value; }
  deserializeAttachment() { return this.attachment; }
}

Use these to test webSocketMessage, webSocketClose, and webSocketError handlers on the DO class without Miniflare overhead. Combine with a fake DurableObjectStorage (in-memory Map) for state persistence tests.

WebSocket checklist

• Upgrade returns 101 with valid auth
• Upgrade returns 401 without auth
• Client receives initial state after connect
• Client sends event → server processes → state updates
• Multiple clients receive broadcasts
• Client disconnect triggers cleanup (webSocketClose)
• Reconnection with checksum resumes without full state replay
• Binary message support (if applicable)

Mocking outbound fetch

When your Worker calls external APIs, use fetchMock from cloudflare:test (an undici MockAgent) to intercept outbound requests without hitting real services.

import { fetchMock } from "cloudflare:test";
import { beforeAll, afterEach, it, expect } from "vitest";

beforeAll(() => {
  fetchMock.activate();
  fetchMock.disableNetConnect(); // throw if an outbound request isn't mocked
});

afterEach(() => fetchMock.assertNoPendingInterceptors());

it("proxies to external API and transforms response", async () => {
  fetchMock
    .get("https://api.stripe.com")
    .intercept({ path: "/v1/charges/ch_123" })
    .reply(200, JSON.stringify({ id: "ch_123", amount: 2000, currency: "usd" }));

  const res = await SELF.fetch("https://api.test/api/v1/charges/ch_123", { headers });
  expect(res.status).toBe(200);

  const body = (await res.json()) as { chargeId: string; amount: number };
  expect(body.chargeId).toBe("ch_123");
  expect(body.amount).toBe(2000);
});

it("handles external API errors gracefully", async () => {
  fetchMock
    .get("https://api.stripe.com")
    .intercept({ path: "/v1/charges/ch_bad" })
    .reply(500, "Internal Server Error");

  const res = await SELF.fetch("https://api.test/api/v1/charges/ch_bad", { headers });
  expect(res.status).toBe(502); // or whatever your error mapping returns
});

Key rules:

• Always call fetchMock.activate() in beforeAll and fetchMock.assertNoPendingInterceptors() in afterEach
• fetchMock.disableNetConnect() ensures no unmocked requests leak through
• This only mocks fetch in the test runner Worker — auxiliary Workers need Miniflare's fetchMock/outboundService options

Testing handler functions directly

For lightweight tests that skip the HTTP layer, use createExecutionContext and waitOnExecutionContext:

import { env, createExecutionContext, waitOnExecutionContext } from "cloudflare:test";
import worker from "./index";

it("calls fetch handler directly", async () => {
  const request = new Request("https://example.com/api/health");
  const ctx = createExecutionContext();
  const response = await worker.fetch(request, env, ctx);
  await waitOnExecutionContext(ctx); // waits for all ctx.waitUntil() promises
  expect(response.status).toBe(200);
});

Testing scheduled handlers (Cron Triggers)

import { env, createScheduledController, createExecutionContext, waitOnExecutionContext } from "cloudflare:test";
import worker from "./index";

it("runs scheduled cleanup job", async () => {
  const ctrl = createScheduledController({
    scheduledTime: new Date(1000),
    cron: "0 0 * * *", // daily midnight
  });
  const ctx = createExecutionContext();
  await worker.scheduled(ctrl, env, ctx);
  await waitOnExecutionContext(ctx);

  // Verify side effect — e.g. expired rows cleaned up
  const remaining = await env.DB.prepare(
    "SELECT count(*) as cnt FROM sessions WHERE expired = 1"
  ).first<{ cnt: number }>();
  expect(remaining?.cnt).toBe(0);
});

Testing Queue consumers

import { env, createMessageBatch, createExecutionContext, getQueueResult } from "cloudflare:test";
import worker from "./index";

it("processes queue messages and acks", async () => {
  const batch = createMessageBatch("my-queue", [
    { id: "msg-1", timestamp: new Date(1000), body: { userId: "user-1", action: "signup" } },
    { id: "msg-2", timestamp: new Date(2000), body: { userId: "user-2", action: "signup" } },
  ]);
  const ctx = createExecutionContext();
  await worker.queue(batch, env, ctx);
  const result = await getQueueResult(batch, ctx);

  expect(result.ackAll).toBe(false);
  expect(result.explicitAcks).toStrictEqual(["msg-1", "msg-2"]);
  expect(result.retryMessages).toStrictEqual([]);
});

it("retries failed messages", async () => {
  const batch = createMessageBatch("my-queue", [
    { id: "msg-bad", timestamp: new Date(1000), body: { invalid: true } },
  ]);
  const ctx = createExecutionContext();
  await worker.queue(batch, env, ctx);
  const result = await getQueueResult(batch, ctx);

  expect(result.retryMessages).toStrictEqual(["msg-bad"]);
});

Testing Durable Objects directly

Use runInDurableObject to reach inside a DO instance for seeding, spying, or asserting on persisted state:

import { env, runInDurableObject, runDurableObjectAlarm, listDurableObjectIds } from "cloudflare:test";
import { Counter } from "./index";

it("increments and persists count", async () => {
  const id = env.COUNTER.newUniqueId();
  const stub = env.COUNTER.get(id);

  let response = await stub.fetch("https://example.com");
  expect(await response.text()).toBe("1");

  // Reach inside the DO to verify storage
  response = await runInDurableObject(stub, async (instance: Counter, state) => {
    expect(instance).toBeInstanceOf(Counter);
    expect(await state.storage.get<number>("count")).toBe(1);
    return instance.fetch(new Request("https://example.com"));
  });
  expect(await response.text()).toBe("2");
});

it("runs scheduled alarm", async () => {
  const id = env.COUNTER.newUniqueId();
  const stub = env.COUNTER.get(id);
  await stub.fetch("https://example.com/schedule-cleanup");

  const alarmRan = await runDurableObjectAlarm(stub);
  expect(alarmRan).toBe(true);
});

it("lists created DO instances (respects isolatedStorage)", async () => {
  const id = env.COUNTER.newUniqueId();
  const stub = env.COUNTER.get(id);
  await stub.fetch("https://example.com");

  const ids = await listDurableObjectIds(env.COUNTER);
  expect(ids.length).toBe(1);
  expect(ids[0].equals(id)).toBe(true);
});

D1 migrations in tests

Use applyD1Migrations with readD1Migrations for projects using D1's migration system:

// vitest.config.ts
import { defineWorkersConfig, readD1Migrations } from "@cloudflare/vitest-pool-workers/config";
import path from "node:path";

export default defineWorkersConfig({
  test: {
    setupFiles: ["./test/apply-migrations.ts"],
    poolOptions: {
      workers: {
        miniflare: {
          d1Databases: { DB: "test-db" },
        },
      },
    },
  },
});

// test/apply-migrations.ts
import { env, applyD1Migrations } from "cloudflare:test";
import migrations from "../migrations"; // readD1Migrations output injected via config

await applyD1Migrations(env.DB, migrations);

Testing Workflows

Use workflow introspectors to control timing, mock steps, and assert outcomes:

import { env, introspectWorkflowInstance, SELF } from "cloudflare:test";

it("completes approval workflow with mocked event", async () => {
  await using instance = await introspectWorkflowInstance(env.MY_WORKFLOW, "wf-123");

  await instance.modify(async (m) => {
    await m.disableSleeps(); // all sleeps resolve instantly
    await m.mockEvent({
      type: "user-approval",
      payload: { approved: true, approverId: "user-1" },
    });
  });

  await env.MY_WORKFLOW.create({ id: "wf-123" });

  await expect(instance.waitForStatus("complete")).resolves.not.toThrow();
  const output = await instance.getOutput();
  expect(output).toEqual({ success: true });
  // dispose is automatic via `await using`
});

it("handles step failure with retry", async () => {
  await using instance = await introspectWorkflowInstance(env.MY_WORKFLOW, "wf-456");

  await instance.modify(async (m) => {
    await m.disableSleeps();
    // Fail payment step once, then succeed on retry
    await m.mockStepError(
      { name: "process-payment" },
      new Error("Gateway timeout"),
      1, // fail only first attempt
    );
    await m.mockEvent({ type: "user-approval", payload: { approved: true } });
  });

  await env.MY_WORKFLOW.create({ id: "wf-456" });
  await expect(instance.waitForStatus("complete")).resolves.not.toThrow();
});

For workflows where instance IDs are unknown (created inside the Worker):

import { env, introspectWorkflow, SELF } from "cloudflare:test";

it("captures all workflow instances triggered by fetch", async () => {
  await using introspector = await introspectWorkflow(env.MY_WORKFLOW);

  await introspector.modifyAll(async (m) => {
    await m.disableSleeps();
    await m.mockEvent({ type: "approval", payload: { approved: true } });
  });

  // Trigger workflow creation via HTTP
  await SELF.fetch("https://api.test/api/v1/start-batch");

  const instances = await introspector.get();
  for (const instance of instances) {
    await expect(instance.waitForStatus("complete")).resolves.not.toThrow();
  }
});

Workflow modifier methods:

• disableSleeps(steps?) — resolve step.sleep() / step.sleepUntil() instantly
• mockStepResult(step, result) — return value without running the step
• mockStepError(step, error, times?) — force step to throw (N times or forever)
• forceStepTimeout(step, times?) — simulate step timeout
• mockEvent(event) — satisfy a step.waitForEvent()
• forceEventTimeout(step) — simulate event timeout

Always dispose introspectors (await using or explicit .dispose()) to prevent state leaking between tests with isolatedStorage.

Hyperdrive (Postgres) variant

When the Worker uses Hyperdrive instead of D1:

// vitest.config.ts
export default defineWorkersConfig(async () => {
  return {
    test: {
      globalSetup: ["./src/__tests__/global-setup.ts"], // starts pgmock
      setupFiles: ["./src/__tests__/apply-migrations.ts"],
      poolOptions: {
        workers: ({ inject }) => {
          const connectionString = inject("pgmockConnectionString");
          return {
            wrangler: { configPath: "./wrangler.jsonc", environment: "development" },
            miniflare: {
              hyperdrives: { HYPERDRIVE: `${connectionString}/postgres` },
            },
            isolatedStorage: true,
            singleWorker: true,
          };
        },
      },
    },
  };
});

Binding verification uses Drizzle or raw SQL through the Hyperdrive binding instead of env.DB.prepare().

Integration with autonomous loops

For /nightshift and /ralph-tdd

When the current task involves a Cloudflare Worker:

1. Check for existing vitest.integration.config.* — if missing, create one using the setup above
2. For each route touched by the current task, write integration tests before implementation (TDD)
3. Run pnpm test:integration as the primary feedback command
4. Integration tests count toward acceptance criteria — a route without integration tests is not done

For /swarm

• Feature agent: Writes integration tests as part of TDD (red → green → refactor)
• CRAP agent: Flags untested routes/endpoints as high-CRAP targets
• Mutation agent: Runs Stryker against integration tests — surviving mutants in route handlers indicate weak assertions
• Acceptance agent: Integration tests ARE the acceptance layer for API Workers (no Playwright needed for pure API services)

Test organization

test/
  integration/
    setup.ts                    # Schema + seed data
    auth.test.ts                # Auth middleware tests
    items.test.ts               # /api/v1/items CRUD
    items-validation.test.ts    # Input validation edge cases
    health.test.ts              # Health/status endpoints

Or colocated:

src/
  routes/
    items/
      index.ts
      __tests__/
        items.test.ts

Gotchas

• Check .dev.vars AND GitHub Actions secrets independently. A test that passes locally with .dev.vars can fail in CI if GH Actions doesn't have the same secrets configured.
• isolatedStorage: true means each test starts clean. If you seed data in beforeEach, it only exists for that test. Don't rely on data from a previous test.
• Miniflare bindings are real but local. They behave like production bindings but data doesn't persist between test runs. Don't confuse Miniflare state with production state.
• wrangler.toml vs wrangler.jsonc — the vitest config must point to whichever config file your project actually uses. A mismatch means no bindings in tests.
• Hyperdrive tests need a running Postgres. Unlike D1 (which is SQLite-backed locally), Hyperdrive tests need pgmock or a real Postgres instance. The globalSetup file must start it before tests run.
• fetchMock only mocks fetch in the test Worker. If your Worker delegates to auxiliary Workers, those Workers' fetch calls are NOT mocked. Use Miniflare's outboundService for auxiliary Worker mocking.

Checklist for each endpoint

• Happy path (correct input → expected output + binding state)
• Auth: missing, invalid, expired
• Validation: missing fields, wrong types, boundary values
• Not found (404)
• Idempotency where applicable (DELETE twice, PUT same data)
• Side effects verified in binding (D1 row, KV key, R2 object)