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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:

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

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

Tests can be grouped into suites with describe.

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.

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

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

Setup and teardown

Perform per-test setup and teardown logic with beforeEach and afterEach.

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

beforeEach(() => {
  console.log("running test.");
});

afterEach(() => {
  console.log("done with test.");
});

// tests...

Perform per-scope setup and teardown logic with beforeAll and afterAll. At the top-level, the scope is the current file; in a describe block, the scope is the block itself.

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

let db: Database;
beforeAll(() => {
  // connect to database
  db = initializeDatabase();
});

afterAll(() => {
  // close connection
  db.close();
});

// tests...