# Migrate from Jest to Bun's test runner

In many cases, Bun's test runner can run Jest test suites with no code changes. Run `bun test` instead of `npx jest` or `yarn test`.

```sh terminal icon="terminal"
npx jest # [!code --]
yarn test # [!code --]
bun test # [!code ++]
```

---

Your test files usually work as-is.

- Bun internally rewrites imports from `@jest/globals` to their `bun:test` equivalents.
- If you rely on Jest to inject globals like `test` and `expect`, Bun does that too.

If you'd rather import from `bun:test` directly, update the imports.

```ts title="test.ts" icon="/icons/typescript.svg"
import { test, expect } from "@jest/globals"; // [!code --]
import { test, expect } from "bun:test"; // [!code ++]
```

---

Since Bun v1.2.19, a triple-slash directive enables **TypeScript support** for global test functions. Add it to _one file_ in your project, such as:

- A `global.d.ts` file in your project root
- Your test `preload.ts` setup file (if using `preload` in bunfig.toml)
- Any single `.ts` file that TypeScript includes in your compilation

```ts title="global.d.ts" icon="/icons/typescript.svg"
/// <reference types="bun-types/test-globals" />
```

---

Once added, every test file in your project gets TypeScript support for the Jest globals:

```ts math.test.ts icon="/icons/typescript.svg"
describe("my test suite", () => {
  test("should work", () => {
    expect(1 + 1).toBe(2);
  });

  beforeAll(() => {
    // setup code
  });

  afterEach(() => {
    // cleanup code
  });
});
```

---

Bun implements most of Jest's matchers, but compatibility isn't 100%. See the compatibility table in [Writing tests](/test/writing-tests#matchers).

---

If you use `testEnvironment: "jsdom"` to run your tests in a browser-like environment, follow the [DOM testing with Bun and happy-dom](/guides/test/happy-dom) guide to inject browser APIs into the global scope. That guide uses [`happy-dom`](https://github.com/capricorn86/happy-dom), a leaner and faster alternative to [`jsdom`](https://github.com/jsdom/jsdom).

```toml bunfig.toml icon="settings"
[test]
preload = ["./happydom.ts"]
```

---

Replace `bail` in your Jest config with the `--bail` CLI flag.

```sh terminal icon="terminal"
bun test --bail=3
```

---

Replace `collectCoverage` with the `--coverage` CLI flag.

```sh terminal icon="terminal"
bun test --coverage
```

---

Replace `testTimeout` with the `--timeout` CLI flag.

```sh terminal icon="terminal"
bun test --timeout 10000
```

---

Many other Jest settings are irrelevant in `bun test`.

- `transform` — Bun supports TypeScript & JSX. Configure other file types with [plugins](/runtime/plugins).
- `extensionsToTreatAsEsm`
- `haste` — Bun uses its own [module resolver](/runtime/module-resolution)
- `watchman`, `watchPlugins`, `watchPathIgnorePatterns` — use `--watch` to run tests in watch mode
- `verbose` — `bun test` reports each test by default. Use `--only-failures` or `--dots` for less output (see [Test reporters](/test/reporters)).

---

Many other settings have an equivalent in the `[test]` section of `bunfig.toml`. For example:

- `setupFiles`/`setupFilesAfterEnv` → `preload`
- `testPathIgnorePatterns` → `pathIgnorePatterns`
- `rootDir` → `root`
- `coverageDirectory` → `coverageDir`
- `coverageReporters` → `coverageReporter`
- `coverageThreshold` → `coverageThreshold` (as a fraction like `0.9`, not a percentage)

See [Test configuration](/test/configuration). Settings without an equivalent are not supported. [File a feature request](https://github.com/oven-sh/bun/issues/new?template=4-feature-request.yml) if something you need is missing.

---

See also:

- [Mark a test as a todo](/guides/test/todo-tests)
- [Writing tests](/test/writing-tests)