# deride

> TypeScript-first mocking library that wraps rather than monkey-patches. Works with frozen objects, sealed classes, and any coding style.

Zero runtime dependencies beyond `debug`. Ships ESM + CJS + `.d.ts`. Framework-agnostic; opt-in integrations for vitest / jest / fake timers via sub-paths.

This site also publishes:

- [`llms-full.txt`](https://guzzlerio.github.io/deride/deride/llms-full.txt) — every page concatenated for single-fetch ingestion.
- `.md` variants of every page (append `.md` to any URL, e.g. https://guzzlerio.github.io/deride/deride/guide/quick-start.md).
- Decision tree, common mistakes, and canonical examples under the [For Agents](https://guzzlerio.github.io/deride/deride/ai/) section.

## Guide

- [Configuring behaviour](https://guzzlerio.github.io/deride/deride/guide/configuring-behaviour.md): Every mocked method has a .setup handle. Call a method on .setup to configure how the mock responds. Setup methods chain (return the setup object) so you can combine .when(...), .once()/.times(n), and
- [Creating mocks](https://guzzlerio.github.io/deride/deride/guide/creating-mocks.md): Five factories cover every shape of test double deride supports. Pick the one that matches what you have.
- [Diagnostics](https://guzzlerio.github.io/deride/deride/guide/diagnostics.md): When an assertion fails, you want to see what actually happened — not just that it didn't match. deride's failure messages include the full recorded call history, with indices.
- [Writing expectations](https://guzzlerio.github.io/deride/deride/guide/expectations.md): Every mocked method exposes an .expect.<method> handle with three branches:
- [Installation](https://guzzlerio.github.io/deride/deride/guide/installation.md): - Node.js 20 or later (deride's published CI matrix is Node 20 / 22 × Ubuntu / macOS / Windows).
- [Introduction](https://guzzlerio.github.io/deride/deride/guide/introduction.md): deride is a TypeScript-first mocking library that works with frozen objects, sealed classes, and any coding style — because it composes rather than monkey-patches.
- [Lifecycle management](https://guzzlerio.github.io/deride/deride/guide/lifecycle.md): Two concerns live here: resetting call history between tests, and snapshotting/restoring a mock's full state (behaviours + calls) to roll back in-test changes.
- [Argument matchers](https://guzzlerio.github.io/deride/deride/guide/matchers.md): deride's match.* namespace gives you composable, brand-tagged predicates that work in every place a value can appear:
- [Migrating](https://guzzlerio.github.io/deride/deride/guide/migrating.md): Common patterns from other mocking libraries, translated to deride.
- [Cross-mock ordering](https://guzzlerio.github.io/deride/deride/guide/ordering.md): Sometimes it's not enough to assert that a call happened — you need to assert that it happened before or after another call on a different mock. inOrder(...) is the tool.
- [Philosophy](https://guzzlerio.github.io/deride/deride/guide/philosophy.md): deride is built on one idea: composition, not monkey-patching. This page explains what that means, why it matters, and the two subtler design rules that fall out of it — the dispatch model, and the ex
- [Quick Start](https://guzzlerio.github.io/deride/deride/guide/quick-start.md): A five-minute tour of the API through a realistic scenario: testing a UserService that depends on a Database.
- [Spy inspection](https://guzzlerio.github.io/deride/deride/guide/spy.md): Every mocked method has a .spy handle alongside .setup and .expect. The spy API is read-only and never throws — it gives you the call history as structured data to inspect, feed forward, or snapshot.
- [TypeScript](https://guzzlerio.github.io/deride/deride/guide/typescript.md): deride is TypeScript-first. Every public API is generic over the shape you're mocking, so setup methods are constrained to the real method signatures and return types.

## Integrations

- [`deride/clock` — fake timers](https://guzzlerio.github.io/deride/deride/integrations/clock.md): A lightweight, dependency-free fake-timers helper. Pairs well with setup.toResolveAfter / toRejectAfter / toHang when you want synchronous control over Date.now, setTimeout, setInterval, and queueMicr
- [`deride/jest` — jest matchers](https://guzzlerio.github.io/deride/deride/integrations/jest.md): Same matcher set as deride/vitest, registered via jest's expect.extend. Import once (ideally from setupFilesAfterEach) and the matchers become available on every test.
- [`deride/vitest` — vitest matchers](https://guzzlerio.github.io/deride/deride/integrations/vitest.md): Opt-in toHaveBeenCalled* matcher family that integrates deride's spy API with vitest's expect. Import once — typically from a setupFiles — and the matchers become available globally on every spy and M

## API reference

- [API Reference](https://guzzlerio.github.io/deride/deride/api/index.md): Quick index of every public export from deride and its sub-paths.
- [`func`](https://guzzlerio.github.io/deride/deride/api/func.md): Create a standalone mocked function. If original is supplied, the mock falls back to calling it when no behaviour matches; otherwise the unconfigured mock returns undefined.
- [`inOrder`](https://guzzlerio.github.io/deride/deride/api/in-order.md): Assert that spies fired in a relative order.
- [`match`](https://guzzlerio.github.io/deride/deride/api/match.md): Namespace of composable argument matchers. Usable everywhere a value can appear: setup.when, expect.*.withArg, withArgs, matchExactly, withReturn, threw, and nested inside objects/arrays at any depth.
- [`sandbox`](https://guzzlerio.github.io/deride/deride/api/sandbox.md): Create a scope that registers every mock created through its factories. reset() clears call history on all of them; restore() clears behaviours too.
- [`stub`](https://guzzlerio.github.io/deride/deride/api/stub.md): Build a test double from method names, an object, or a class.
- [Types](https://guzzlerio.github.io/deride/deride/api/types.md): Every public type exported from deride, grouped by concern.
- [`wrap`](https://guzzlerio.github.io/deride/deride/api/wrap.md): Wrap an existing object (or function) with deride facades. Unlike stub, the real methods still run by default — wrap is the tool for partial mocking.

## Recipes

- [Async & Promises](https://guzzlerio.github.io/deride/deride/recipes/async-mocking.md): Patterns for mocking async APIs: resolving with data, rejecting, delaying, hanging, and asserting against the captured Promise.
- [Fluent / chainable APIs](https://guzzlerio.github.io/deride/deride/recipes/chainable-apis.md): Query builders, jQuery-style chains, builder patterns, fluent assertion libraries — all involve methods that return this. toReturnSelf() is the tool.
- [Class mocking](https://guzzlerio.github.io/deride/deride/recipes/class-mocking.md): Three patterns, in order of preference.
- [Module mocking](https://guzzlerio.github.io/deride/deride/recipes/module-mocking.md): deride creates mock objects; your test runner handles substituting them at import time. Use the two together.
- [Time & timers](https://guzzlerio.github.io/deride/deride/recipes/time-and-timers.md): Three tools cover the time axis: