Installation

Requirements

• Node.js 20 or later (deride's published CI matrix is Node 20 / 22 × Ubuntu / macOS / Windows).
• A test runner that catches thrown errors — vitest, jest, mocha, node:test, uvu, bun test, etc. deride is framework-agnostic.

Install

pnpm

pnpm add -D deride

npm

npm install --save-dev deride

yarn

yarn add -D deride

bun

bun add -d deride

deride itself has a single runtime dependency (debug) and ships ESM + CJS + .d.ts for every entry point.

Import

The main entry exports the full API, plus a deride convenience namespace:

import { stub, wrap, func, match, inOrder, sandbox } from 'deride'
// or
import deride from 'deride'
deride.stub(...)

Sub-paths

Three optional integrations live under sub-paths. They're opt-in so the core bundle stays small:

import { useFakeTimers } from 'deride/clock'   // fake timers
import 'deride/vitest'                          // vitest matchers (side-effect)
import 'deride/jest'                            // jest matchers (side-effect)

The deride/vitest and deride/jest imports register toHaveBeenCalled* matchers on your test runner's expect. Load them once — typically from your test-runner's setupFiles. Full details in Integrations.

Peer dependencies

• vitest ≥ 1 if using deride/vitest
• jest ≥ 29 (and @jest/globals) if using deride/jest

These are declared as optional peers — install whichever you use.

TypeScript

All public APIs ship their .d.ts. No additional @types/... package is required.

import { stub, type Wrapped } from 'deride'

interface Service {
  greet(name: string): string
}

const mock: Wrapped<Service> = stub<Service>(['greet'])
mock.setup.greet.toReturn('hello')   // ✓ constrained to string
mock.setup.greet.toReturn(123)       // ✗ type error

See the TypeScript guide for the full story.

Verifying the install

Drop this into a test file and run your suite:

import { describe, it, expect } from 'vitest'   // or jest / node:test
import { func } from 'deride'

describe('deride is installed', () => {
  it('records calls', () => {
    const fn = func<(x: number) => number>()
    fn.setup.toReturn(42)
    expect(fn(1)).toBe(42)
    fn.expect.called.once()
  })
})

If it runs green, you're done. On to the quick start.