manten

name: manten description: Manten testing library patterns - standalone imports via AsyncLocalStorage, async tests, describe groups, hooks, snapshots, timeouts, retries, and concurrency. Use when writing tests with manten, running node test files, or setting up a no-config test suite.

Quick Reference

All APIs are standalone imports:

import {
    test, describe, expect, skip, onTestFail, onTestFinish, onFinish, expectSnapshot
} from 'manten'

Each function automatically knows which test or group it belongs to via AsyncLocalStorage.

Core Pattern: Await Controls Flow

import { test, expect } from 'manten'

// Concurrent (recommended default)
test('A', async () => { /* ... */ })
test('B', async () => { /* runs simultaneously with A */ })

// Sequential: only await when you need ordering
await test('first', async () => { /* ... */ })
await test('second', async () => { /* runs after first */ })

Node.js won't exit while promises are settling, so you don't need await to keep the process alive — only to enforce ordering.

Describe Blocks

import { describe, test } from 'manten'

describe('Auth', () => {
    test('login', async () => { /* ... */ })
    test('logout', async () => { /* ... */ })
})

Nesting:

describe('Outer', () => {
    test('A', () => { /* ... */ })

    describe('Inner', () => {
        test('B', () => { /* ... */ })
    })
})

Awaiting a group waits for all children:

await describe('Group', () => {
    test('A', async () => { /* ... */ })
    test('B', async () => { /* ... */ })
})
// Both A and B complete before continuing

Timeouts & Retries

test() and describe() callbacks always receive { signal } — an AbortSignal that aborts on timeout or when the parent group is aborted:

// Timeout (3rd arg as number)
test('fast test', async ({ signal }) => {
    await fetch('/api', { signal })
}, 1000)

// Options object
test('flaky test', async () => {
    await unreliableAPI()
}, {
    timeout: 5000,
    retry: 3
})

Hooks

import { test, onTestFail, onTestFinish } from 'manten'

test('with cleanup', async () => {
    const resource = await createResource()
    onTestFinish(() => resource.cleanup()) // Always runs
    onTestFail(error => console.log('Debug:', error))
})

onFinish runs after all tests in a describe():

import { describe, test, onFinish } from 'manten'

describe('Database', async () => {
    const database = await connect()
    onFinish(() => database.close())

    test('query', () => { /* ... */ })
})

Hook errors are logged but don't fail the test. onFinish errors set process.exitCode = 1.

Skipping

import { test, skip } from 'manten'

test('linux only', () => {
    if (process.platform !== 'linux') {
        skip('Only runs on Linux')
    }
    // ...
})

Skip entire groups — skip() must be called before any test() or nested describe():

describe('GPU tests', () => {
    if (!hasGPU) {
        skip('GPU not available')
    }
    test('render', () => { /* ... */ }) // All skipped
})

Concurrency Control

describe('Database tests', () => {
    test('query 1', async () => { /* ... */ })
    test('query 2', async () => { /* ... */ })
    test('query 3', async () => { /* ... */ })
}, { parallel: 2 }) // Max 2 concurrent

Options: false (sequential), true (unbounded), number (limit), 'auto' (adapts to CPU load).

Tests that you explicitly await bypass the parallel queue.

Group Timeouts

describe('Suite', () => {
    test('A', async () => { /* ... */ })
    test('B', async () => { /* ... */ })
}, { timeout: 10_000 })

Individual test timeouts still apply — whichever is stricter wins.

Snapshot Testing

import { test, expectSnapshot } from 'manten'

test('user data', () => {
    // Named (recommended) — order-independent
    expectSnapshot(getUser(), 'initial user')

    // Auto-numbered — keys become "user data 1", "user data 2", etc.
    expectSnapshot(getUser())
})

Snapshots are stored in .manten.snap by default. Serialized with util.inspect — output may differ across Node.js versions, so regenerate after upgrading Node.

Update snapshots: MANTEN_UPDATE_SNAPSHOTS=1 node tests/index.ts

Configure path via configure() or MANTEN_SNAPSHOT_PATH env var:

import { configure } from 'manten'

configure({ snapshotPath: 'custom.snap' })

Splitting Tests Across Files

Import files inside describe() — they automatically nest under the parent group:

// tests/index.ts
import { describe } from 'manten'

describe('my-app', async () => {
    import('./specs/auth.ts')
    import('./specs/api.ts')

    // Or add `await` to run files sequentially
})

// tests/specs/auth.ts
import { describe, test, expect } from 'manten'

describe('Authentication', () => {
    test('login', () => { /* ... */ })
    test('logout', () => { /* ... */ })
})

Each file works standalone too — node tests/specs/auth.ts runs just that file.

Parameterized Test Files

Export a function wrapping describe() to pass data into test files:

// tests/specs/builds.ts
import { describe, test, expect } from 'manten'

export const builds = (nodePath: string) => describe('builds', () => {
    test('compiles', async () => {
        const result = await run(nodePath)
        expect(result.exitCode).toBe(0)
    })
})

Since describe() doesn't run until called, these can be statically imported:

// tests/index.ts
import { builds } from './specs/builds.ts'
import { describe } from 'manten'

describe('my-app', async () => {
    for (const nodeVersion of ['v20', 'v22', 'v24']) {
        const node = await getNode(nodeVersion)
        await describe(`Node ${node.version}`, () => {
            builds(node.path)
        })
    }
})

Export names should match the file name or describe() description.

Recommended Project Structure

tests/
  specs/       # test files
  utils/       # shared test helpers
  fixtures/    # static test data
  index.ts     # entry point — run this

Running Tests

# Run tests (Node 22.6+ runs TypeScript natively)
node tests/index.ts

# Watch mode
node --watch tests/index.ts

# Run specific test by substring match (case-sensitive)
TESTONLY='login' node tests/index.ts

# Update snapshots
MANTEN_UPDATE_SNAPSHOTS=1 node tests/index.ts

Process-Level Timeout

import { setProcessTimeout } from 'manten'

setProcessTimeout(10 * 60 * 1000) // 10 minutes max

Key Behaviors

• Tests run immediately — no collection phase. test() executes as soon as it's called.
• No beforeAll/beforeEach — inline setup in each test, or use describe() + onFinish() for shared resources.
• Exit code — failures set process.exitCode = 1 but don't force-exit. All tests run to completion.
• TESTONLY — matches against full title including describe prefixes (e.g. Auth › login). Case-sensitive.
• signal — always provided to test() and describe() callbacks, not just when timeouts are set.
• skip() in describe — must be called before any test() or nested describe().
• TypeScript — all APIs fully typed. Test and Describe types exported for advanced use cases.

Migrating from v1

For migrating from manten v1 (callback destructuring) to v2 (standalone imports), see MIGRATION.md.

Related

For disposable file system fixtures, use fs-fixture with await using for automatic cleanup.