Bun Test Basics

A practical reference for Bun's built-in test runner that covers the everyday stuff you'll actually use. You get the core syntax for describe/it blocks, common matchers like toBe and toEqual, test modifiers like skip and only, and parameterized tests with test.each. The CLI options section is helpful for setting timeouts and running tests concurrently. It's Jest-compatible, so if you know Jest the transition is smooth. The matcher examples are comprehensive enough that you won't need to context switch to docs for basic assertions. Load this when you're writing tests in Bun and need a quick syntax check or want to remember how test.each works with objects.

skills.sh installs: 375
GitHub stars: 248
last updated: Aug 21, 2026

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Install

$ npx -y skills add secondsky/claude-skills --skill bun-test-basics --agent claude-code

Installs into .claude/skills of the current project.

Files

Bun Test Basics

Bun ships with a fast, built-in, Jest-compatible test runner. Tests run with the Bun runtime and support TypeScript/JSX natively.

Quick Start

# Run all tests
bun test

# Run specific file
bun test ./test/math.test.ts

# Run tests matching pattern
bun test --test-name-pattern "addition"

Writing Tests

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

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

describe("math", () => {
  test("addition", () => {
    expect(1 + 1).toBe(2);
  });

  test("subtraction", () => {
    expect(5 - 3).toBe(2);
  });
});

Test File Patterns

Bun discovers test files matching:

*.test.{js|jsx|ts|tsx}
*_test.{js|jsx|ts|tsx}
*.spec.{js|jsx|ts|tsx}
*_spec.{js|jsx|ts|tsx}

Test Modifiers

// Skip a test
test.skip("not ready", () => {
  // won't run
});

// Only run this test
test.only("focus on this", () => {
  // other tests won't run
});
// NOTE: in Bun 1.3+ `bun test` exits non-zero in CI when a file uses
// `test.only`. Use it for local debugging only — never commit it.

// Placeholder for future test
test.todo("implement later");

SKILL.md on GitHub