Capability index

Stable

The fixture engine is the core; everything else on this page is a capability built on the same runner and the same explicit composition. Each row names the tier that governs it — read Stability, compatibility, and support for what a tier promises.

Capabilities

Capability	Use it for	Tier	Prerequisites	Guide
Fixtures	Typed values with a lifetime: databases, containers, users, clients	Stable	None	The fixture model
Standard fixtures	Isolated tmpdir, env, stdio, clock, seed, and an armed networkGuard	Stable	None	Deterministic tests
Snapshot testing	Compare a value, a file, or a callback result against a stored baseline	Stable	None	Snapshot testing
Property-based testing	State an invariant and let fast-check generate inputs, then shrink failures	Stable	fast-check	Property-based testing
Parameterized tests	Run one body over a fixed matrix of named values through test.prop	Stable	fast-check	Parameterized tests
HTTP mocking and test servers	Serve an ephemeral Bun.serve instance and intercept fetch with MSW-style handlers	Stable	None	HTTP mocking and test servers
Recording HTTP cassettes	Record real HTTP traffic and callback results, then replay them deterministically	Stable	None	Recording HTTP cassettes
DOM testing	Render and query markup in-process with happy-dom	Stable	happy-dom	DOM and browser testing
Browser testing	Drive a real headless Chromium page through Playwright	Experimental	playwright + an installed Chromium build	DOM and browser testing
BDD scenarios	Write one test as fluent given / when / then steps that share typed state	Experimental	@aboviq/bun-test-cucumber	BDD scenarios

Everything above shares one rule: the capability is available where the runner you import has it, and a peer package is loaded only when a requested fixture actually needs it. A unit test that never mentions webPage never loads happy-dom, and a suite that never mentions browserPage never loads Playwright.

Built-in fixtures overview

The root test contributes these nineteen names. Request one by destructuring it; override one with an extension of the same name. Per-fixture members, scopes, and behaviours are in the Built-in fixture API.

Area	Fixtures	What they give a test
Standard	tmpdir, env, stdio, clock, seed, networkGuard	A temporary directory, a scoped environment, captured output streams, frozen time, a seeded Math.random, and a fetch guard — each restored at teardown.
DOM	window, document, page	The happy-dom window and document, plus a small helper for mounting, querying, and clicking.
Either backend	webPage	One page-shaped API that is happy-dom by default and Playwright when BUN_TEST_UTILS_WEB_ENV=browser.
Browser (experimental)	browser, browserContext, browserPage, browserHttpMock	A session-scoped Chromium, a per-test context and page, and httpMock handlers installed on that context.
Server and HTTP	testServer, serverUrl, httpMock	An ephemeral Bun.serve instance on a random port, its URL as a dependency, and MSW-style fetch handlers.
Cassettes	cassette	Callback record/replay plus HTTP record/replay, with serializers.
Snapshots	snapshot	Value, file, and callable snapshot assertions with serializers and modes.

Where to go next

• Nothing is passing yet? Start at Install and first passing test.
• Deciding how much environment to take on? Choose your test environment.
• Bringing in a real resource? Database fixture and Test server and HTTP mocks.
• Blocked by an error? Troubleshooting.