Testing

Unit test individual steps and integration test entire workflows using Vitest and the Vite plugin.

Testing is a critical part of building reliable workflows. Because steps are just functions annotated with directives, they can be unit tested like any other JavaScript function. Workflow DevKit also provides a Vite plugin that integrates with Vitest, enabling full integration tests against a real workflow runtime.

This guide covers two approaches:

Unit testing - Test individual steps as plain functions, without the workflow runtime.
Integration testing - Test entire workflows against a real workflow setup using the Vite plugin. Required for workflows that use hooks, webhooks, sleep(), or retries.

Unit Testing Steps

Without the workflow compiler, the "use step" directive is a no-op. Your step functions run as regular JavaScript functions, making them straightforward to unit test with no special configuration.

Example Steps

Given a workflow file with step functions like this:

workflows/user-signup.ts

import { sleep } from "workflow";

export async function handleUserSignup(email: string) {
  "use workflow";

  const user = await createUser(email);
  await sendWelcomeEmail(user);

  await sleep("5d");
  await sendOnboardingEmail(user);

  return { userId: user.id, status: "onboarded" };
}

export async function createUser(email: string) {
  "use step"; 
  return { id: crypto.randomUUID(), email };
}

export async function sendWelcomeEmail(user: { id: string; email: string }) {
  "use step"; 
  // Send email logic
}

export async function sendOnboardingEmail(user: { id: string; email: string }) {
  "use step"; 
  // Send email logic
}

Writing Unit Tests for Steps

You can import and test step functions directly with Vitest. No special configuration or workflow plugin is needed:

workflows/user-signup.test.ts

import { describe, it, expect } from "vitest";
import { createUser, sendWelcomeEmail } from "./user-signup"; 

describe("createUser step", () => {
  it("should create a user with the given email", async () => {
    const user = await createUser("test@example.com");

    expect(user.email).toBe("test@example.com");
    expect(user.id).toBeDefined();
  });
});

describe("sendWelcomeEmail step", () => {
  it("should send a welcome email without throwing", async () => {
    const user = { id: "user-1", email: "test@example.com" };
    await expect(sendWelcomeEmail(user)).resolves.not.toThrow();
  });
});

This approach is ideal for verifying the business logic inside individual steps in isolation.

Unit testing works well for individual steps. A simple workflow that only calls steps can also be unit tested this way, since "use workflow" is similarly a no-op without the compiler. However, any workflow that uses runtime features like sleep(), hooks, or webhooks cannot be unit tested directly because those APIs require the workflow runtime. Use integration testing for testing entire workflows, especially those that depend on workflow-only features.

Integration Testing with the Vite Plugin

For workflows that rely on runtime features like hooks, webhooks, sleep(), or error retries, you need to test against a real workflow setup. The workflow/vite plugin integrates directly with Vitest, compiling your "use workflow" and "use step" directives so the full workflow runtime is active during tests.

Vitest Configuration

Create a separate Vitest config for integration tests that includes the workflow() plugin and a globalSetup script:

vitest.integration.config.ts

import { defineConfig } from "vitest/config";
import { workflow } from "workflow/vite"; 

export default defineConfig({
  plugins: [workflow()], 
  test: {
    include: ["**/*.integration.test.ts"],
    testTimeout: 60_000, // Workflows may take longer than default timeout
    globalSetup: "./vitest.integration.setup.ts", 
  },
});

Use a separate Vitest configuration and a distinct file naming convention (e.g. *.integration.test.ts) to keep unit tests and integration tests separate. Unit tests run with a standard Vitest config without the workflow plugin, while integration tests use the config above.

Global Setup Script

Integration tests need a running server to execute workflow steps. The globalSetup script starts a Nitro server as a sidecar process before tests run, and tears it down afterwards:

vitest.integration.setup.ts

import { spawn } from "node:child_process";
import { setTimeout as delay } from "node:timers/promises";
import type { ChildProcess } from "node:child_process";

let server: ChildProcess | null = null;
const PORT = "4000";

export async function setup() { 
  console.log("Starting server for workflow execution...");

  server = spawn("npx", ["nitro", "dev", "--port", PORT], {
    stdio: "pipe",
    detached: false,
    env: process.env,
  });

  // Wait for the server to be ready
  const ready = await new Promise<boolean>((resolve) => {
    const timeout = setTimeout(() => resolve(false), 15_000);

    server?.stdout?.on("data", (data) => {
      const output = data.toString();
      console.log("[server]", output);
      if (output.includes("listening") || output.includes("ready")) {
        clearTimeout(timeout);
        resolve(true);
      }
    });

    server?.stderr?.on("data", (data) => {
      console.error("[server]", data.toString());
    });

    server?.on("error", (error) => {
      console.error("Failed to start server:", error);
      clearTimeout(timeout);
      resolve(false);
    });
  });

  if (!ready) {
    throw new Error("Server failed to start within 15 seconds");
  }

  await delay(2_000); // Allow full initialization

  // Point the workflow runtime at the local server
  process.env.WORKFLOW_LOCAL_BASE_URL = `http://localhost:${PORT}`; 
  process.env.WORKFLOW_LOCAL_DATA_DIR = "./.workflow-data"; 

  console.log("Server ready for workflow execution");
}

export async function teardown() { 
  if (server) {
    console.log("Stopping server...");
    server.kill("SIGTERM");
    await delay(1_000);
    if (!server.killed) {
      server.kill("SIGKILL");
    }
  }
}

The setup script sets two environment variables that the workflow runtime reads:

WORKFLOW_LOCAL_BASE_URL tells the runtime where to send step execution requests
WORKFLOW_LOCAL_DATA_DIR tells the runtime where to persist workflow state locally

You can use any server framework that supports the workflow runtime. The example above uses Nitro, but you could also use a Next.js, Hono, or any other supported server.

Running Integration Tests

Add a script to your package.json:

package.json

{
  "scripts": {
    "test": "vitest",
    "test:integration": "vitest --config vitest.integration.config.ts"
  }
}

Testing Hooks and Waits

The real power of integration testing comes when testing workflow-only features. Hooks and waits can be resumed programmatically using the workflow/api functions, making it straightforward to simulate external events in your tests.

Given a workflow that waits for approval via a hook:

workflows/approval.ts

import { createHook } from "workflow";

export async function approvalWorkflow(documentId: string) {
  "use workflow";

  const prepared = await prepareDocument(documentId);

  using hook = createHook<{ approved: boolean; reviewer: string }>({ 
    token: `approval:${documentId}`, 
  }); 

  const decision = await hook; 

  if (decision.approved) {
    await publishDocument(prepared);
    return { status: "published", reviewer: decision.reviewer };
  }

  return { status: "rejected", reviewer: decision.reviewer };
}

async function prepareDocument(documentId: string) {
  "use step";
  return { id: documentId, content: "..." };
}

async function publishDocument(doc: { id: string; content: string }) {
  "use step";
  console.log(`Publishing document ${doc.id}`);
}

You can write an integration test that starts the workflow, resumes the hook programmatically, and asserts the result:

workflows/approval.integration.test.ts

import { describe, it, expect } from "vitest";
import { start, resumeHook } from "workflow/api"; 
import { approvalWorkflow } from "./approval";

describe("approvalWorkflow", () => {
  it("should publish when approved", async () => {
    const run = await start(approvalWorkflow, ["doc-123"]); 

    // Resume the hook programmatically, simulating an external approval
    await resumeHook("approval:doc-123", { 
      approved: true, 
      reviewer: "alice", 
    }); 

    const result = await run.returnValue;
    expect(result).toEqual({
      status: "published",
      reviewer: "alice",
    });
  });

  it("should reject when not approved", async () => {
    const run = await start(approvalWorkflow, ["doc-456"]);

    await resumeHook("approval:doc-456", {
      approved: false,
      reviewer: "bob",
    });

    const result = await run.returnValue;
    expect(result).toEqual({
      status: "rejected",
      reviewer: "bob",
    });
  });
});

start() and resumeHook() are the key API functions for integration testing. Use start() to trigger a workflow and resumeHook() to simulate external events that resume paused hooks. See the API Reference for the full list of available functions.

Debugging Test Runs

When integration tests fail, the Workflow DevKit CLI and Web UI can help you inspect what happened. Because integration tests persist workflow state to WORKFLOW_LOCAL_DATA_DIR, you can use the same observability tools you would use in development.

Launch the Web UI to visually explore your test workflow runs:

npx workflow web

Or use the CLI to inspect runs in the terminal:

# List recent workflow runs
npx workflow inspect runs

# Inspect a specific run
npx workflow inspect runs <run-id>

The Web UI shows each step, its inputs and outputs, retry attempts, hook state, and timing. This is especially useful for diagnosing issues with hooks that were not resumed, steps that failed unexpectedly, or workflows that timed out.

Workflow DevKit Web UI

See the Observability docs for the full set of CLI commands and Web UI features.

Best Practices

Separate Unit and Integration Tests

Keep two test configurations:

Unit tests - Standard Vitest config, no workflow plugin. Fast, no infrastructure required.
Integration tests - Vitest config with workflow() plugin. Tests the full workflow lifecycle including hooks, sleeps, and retries.