Bun

Writing tests

Define tests with a Jest-like API imported from the built-in bun:test module. Long term, Bun aims for complete Jest compatibility; at the moment, a limited set of expect matchers are supported.

Basic usage

To define a simple test:

math.test.ts
import { expect, test } from "bun:test";

test("2 + 2", () => {
  expect(2 + 2).toBe(4);
});

Jest-style globals

Tests can be grouped into suites with describe.

math.test.ts
import { expect, test, describe } from "bun:test";

describe("arithmetic", () => {
  test("2 + 2", () => {
    expect(2 + 2).toBe(4);
  });

  test("2 * 2", () => {
    expect(2 * 2).toBe(4);
  });
});

Tests can be async.

import { expect, test } from "bun:test";

test("2 * 2", async () => {
  const result = await Promise.resolve(2 * 2);
  expect(result).toEqual(4);
});

Alternatively, use the done callback to signal completion. If you include the done callback as a parameter in your test definition, you must call it or the test will hang.

import { expect, test } from "bun:test";

test("2 * 2", done => {
  Promise.resolve(2 * 2).then(result => {
    expect(result).toEqual(4);
    done();
  });
});

Skip individual tests with test.skip. These tests will not be run.

import { expect, test } from "bun:test";

test.skip("wat", () => {
  // TODO: fix this
  expect(0.1 + 0.2).toEqual(0.3);
});

Mark a test as a todo with test.todo. These tests will be run, and the test runner will expect them to fail. If they pass, you will be prompted to mark it as a regular test.

import { expect, test } from "bun:test";

test.todo("fix this", () => {
  myTestFunction();
});

Matchers

Bun implements the following matchers. Full Jest compatibility is on the roadmap; track progress here.