Test Runner

The vtz runtime includes a built-in test runner powered by V8. No extra packages to install, no configuration required.

@vertz/test is a synthetic module provided automatically by the vtz runtime — like node:fs in Node.js. You do not need to run vtz add @vertz/test.

Quick start

Create a test file:

// src/math.test.ts
import { describe, expect, it } from '@vertz/test';
import { add } from './math';

describe('add', () => {
  it('adds two numbers', () => {
    expect(add(1, 2)).toBe(3);
  });

  it('handles negative numbers', () => {
    expect(add(-1, 1)).toBe(0);
  });
});

Run it:

vtz test

That’s it. The runner discovers **/*.test.ts and **/*.test.tsx files automatically.

Writing tests

Structure

Use describe to group tests and it (or test) to define individual test cases:

import { describe, it, test, beforeEach, afterEach } from '@vertz/test';

describe('UserService', () => {
  beforeEach(() => {
    // runs before each test in this block
  });

  afterEach(() => {
    // runs after each test in this block
  });

  it('creates a user', async () => {
    // test implementation
  });

  test('deletes a user', async () => {
    // `test` is an alias for `it`
  });
});

Hooks

beforeEach(fn) — runs before each test in the current describe block
afterEach(fn) — runs after each test
beforeAll(fn) — runs once before all tests in the block
afterAll(fn) — runs once after all tests in the block

Hooks can be async. They compose hierarchically — parent beforeEach runs before child beforeEach.

Modifiers

describe.skip('skipped suite', () => {
  /* ... */
});
describe.only('only this suite runs', () => {
  /* ... */
});

it.skip('skipped test', () => {
  /* ... */
});
it.only('only this test runs', () => {
  /* ... */
});
it.todo('not implemented yet');

Conditional skip

it.skipIf(process.env.CI)('only runs locally', () => {
  // skipped when CI=true
});

Parameterized tests

it.each([
  [1, 1],
  [2, 4],
  [3, 9],
])('square(%s) = %s', (input, expected) => {
  expect(input * input).toBe(expected);
});

Assertions

The expect API is compatible with Vitest. Here are the most common matchers:

import { expect } from '@vertz/test';

// Equality
expect(result).toBe(42); // strict identity (===)
expect(user).toEqual({ name: 'Ada' }); // deep equality
expect(obj).toStrictEqual(expected); // deep equality + constructor check

// Truthiness
expect(value).toBeTruthy();
expect(value).toBeFalsy();
expect(value).toBeNull();
expect(value).toBeUndefined();
expect(value).toBeDefined();

// Numbers
expect(count).toBeGreaterThan(0);
expect(count).toBeLessThanOrEqual(100);
expect(pi).toBeCloseTo(3.14, 2);

// Strings & Arrays
expect(list).toHaveLength(3);
expect(list).toContain('item');
expect(message).toMatch(/hello/i);

// Objects
expect(user).toHaveProperty('email');
expect(response).toMatchObject({ status: 'ok' });
expect(err).toBeInstanceOf(ValidationError);

// Errors
expect(() => parse('{')).toThrow();
expect(() => parse('{')).toThrow('Unexpected token');

// Negation
expect(value).not.toBe(0);

// Async
await expect(fetchUser()).resolves.toEqual({ name: 'Ada' });
await expect(failingOp()).rejects.toThrow('timeout');

Asymmetric matchers

Use inside toEqual, toHaveBeenCalledWith, and other deep-equality matchers:

expect(user).toEqual({
  id: expect.any(String),
  name: 'Ada',
  roles: expect.arrayContaining(['admin']),
  bio: expect.stringContaining('computer scientist'),
});

Available: expect.any(constructor), expect.anything(), expect.objectContaining(), expect.arrayContaining(), expect.stringContaining(), expect.stringMatching().

Mocking

Mock functions

import { mock, expect } from '@vertz/test';

const fn = mock(() => 42);
fn(1, 2);

expect(fn).toHaveBeenCalledWith(1, 2);
expect(fn).toHaveBeenCalledOnce();

Configure return values:

const fetch = mock();
fetch.mockResolvedValue({ data: [] });

const result = await fetch('/api/users');
// result === { data: [] }

Available methods: mockReturnValue, mockReturnValueOnce, mockResolvedValue, mockResolvedValueOnce, mockRejectedValue, mockRejectedValueOnce, mockImplementation, mockImplementationOnce. Inspect calls via fn.mock.calls, fn.mock.results, and fn.mock.lastCall. Clean up with mockClear() (reset call history), mockReset() (clear + reset implementation), or mockRestore() (restore original for spies).

Spying on methods

import { spyOn, expect } from '@vertz/test';

const obj = { greet: (name: string) => `Hello, ${name}` };
const spy = spyOn(obj, 'greet');

obj.greet('Ada');
expect(spy).toHaveBeenCalledWith('Ada');

spy.mockRestore(); // restores original method

vi namespace

For Vitest compatibility, the vi object provides the same utilities:

import { vi } from '@vertz/test';

// Create mocks
const fn = vi.fn(() => 42);
const spy = vi.spyOn(console, 'log');

// Manage all mocks
vi.clearAllMocks(); // clear call history
vi.resetAllMocks(); // clear + reset implementations
vi.restoreAllMocks(); // restore all spied methods

// Module mocking
vi.mock('./db', () => ({ query: vi.fn() }));
const actual = await vi.importActual('./db');

Fake timers

import { vi, expect } from '@vertz/test';

vi.useFakeTimers();

const callback = vi.fn();
setTimeout(callback, 1000);

vi.advanceTimersByTime(1000);
expect(callback).toHaveBeenCalled();

vi.setSystemTime(new Date('2026-01-01'));
expect(Date.now()).toBe(new Date('2026-01-01').getTime());

vi.useRealTimers();

Available timer methods: useFakeTimers, useRealTimers, advanceTimersByTime, advanceTimersToNextTimer, runAllTimers, runOnlyPendingTimers, setSystemTime, getTimerCount, isFakeTimers.

Configuration

Configure the test runner in vertz.config.ts:

export default {
  test: {
    include: ['src/**/*.test.ts'],
    exclude: ['**/*.local.ts'],
    timeout: 10000, // per-test timeout in ms
    concurrency: 4, // max parallel test files
    reporter: 'terminal', // terminal | json | junit
    coverage: false, // enable coverage collection
    coverageThreshold: 95, // minimum coverage %
    preload: ['./test-setup.ts'], // setup files loaded before tests
  },
};

All fields are optional. Without a config file, vtz test uses sensible defaults.

CLI reference

vtz test [PATH...] [OPTIONS]

Option	Description
`[PATH...]`	Specific files or directories to test (default: project root)
`--filter <str>`	Filter tests by name substring
`--watch`	Re-run tests when files change
`--coverage`	Collect V8 code coverage (outputs `coverage.lcov`)
`--coverage-threshold <n>`	Minimum coverage percentage as integer (default: 95)
`--timeout <ms>`	Per-test timeout in milliseconds (default: 5000)
`--concurrency <n>`	Max parallel test files (default: CPU count)
`--reporter <fmt>`	Output format: `terminal`, `json`, or `junit`
`--bail`	Stop after the first failure
`--no-preload`	Skip preload scripts from config
`--no-cache`	Skip compilation cache
`--root-dir <path>`	Workspace root for module resolution

Examples

# Run a single file
vtz test src/math.test.ts

# Filter by test name
vtz test --filter "creates a user"

# Watch mode
vtz test --watch

# Coverage with threshold
vtz test --coverage --coverage-threshold 95

Coming from Vitest or Jest

The @vertz/test API is intentionally compatible with Vitest. Your test logic stays the same — only the import path and runner change.

	Vitest	Vertz
Import	`import { describe, it, expect } from 'vitest'`	`import { describe, it, expect } from '@vertz/test'`
Config	`vitest.config.ts`	`vertz.config.ts`
Run	`npx vitest`	`vtz test`
Install	`npm add -D vitest`	Nothing — built into the runtime

Key differences

No package to install. @vertz/test is provided by the vtz runtime automatically.
Runs in V8, not Node.js. The test runner uses the same V8 engine as vtz dev.
Snapshot testing (toMatchSnapshot, toMatchInlineSnapshot) is not currently supported.

Migrating from bun:test

The vtz migrate-tests command rewrites imports from bun:test to @vertz/test and adjusts API differences:

vtz migrate-tests              # migrate all test files
vtz migrate-tests --dry-run    # preview changes without writing

Troubleshooting

“Cannot find module ‘@vertz/test’” — You’re running tests with a different runner (Node, Bun, Vitest). Use vtz test instead — @vertz/test is only available inside the vtz runtime. Coverage output — vtz test --coverage generates a coverage.lcov file in the project root. Use any LCOV-compatible viewer to inspect results.

Quick start

Writing tests

Structure

Hooks

Modifiers

Conditional skip

Parameterized tests

Assertions

Asymmetric matchers

Mocking

Mock functions

Spying on methods

vi namespace

Fake timers

Configuration

CLI reference

Examples

Coming from Vitest or Jest

Key differences

Migrating from bun:test

Troubleshooting

Next steps

Server Testing

E2E Testing

​Quick start

​Writing tests

​Structure

​Hooks

​Modifiers

​Conditional skip

​Parameterized tests

​Assertions

​Asymmetric matchers

​Mocking

​Mock functions

​Spying on methods

​vi namespace

​Fake timers

​Configuration

​CLI reference

​Examples

​Coming from Vitest or Jest

​Key differences

​Migrating from bun:test

​Troubleshooting

​Next steps

Server Testing

E2E Testing

Quick start

Writing tests

Structure

Hooks

Modifiers

Conditional skip

Parameterized tests

Assertions

Asymmetric matchers

Mocking

Mock functions

Spying on methods

vi namespace

Fake timers

Configuration

CLI reference

Examples

Coming from Vitest or Jest

Key differences

Migrating from bun:test

Troubleshooting

Next steps