Unit Testing Framework

This walks Claude through writing proper unit tests with the AAA pattern across Jest, pytest, JUnit, and RSpec. You get concrete examples for each language, guidance on mocking and test doubles, and patterns for async code and edge cases. The best practices section is solid on fundamentals like testing one thing per test and keeping tests fast. Most useful when you're setting up testing standards for a project or need Claude to generate comprehensive test suites rather than quick validation code. The reference guides cover the specifics you'd actually need to implement TDD properly instead of just checking if something doesn't crash.

skills.sh installs: 622
GitHub stars: 379
last updated: Aug 21, 2026

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Install

$ npx -y skills add aj-geddes/useful-ai-prompts --skill unit-testing-framework --agent claude-code

Installs into .claude/skills of the current project.

Files

Overview

Write effective unit tests that are fast, isolated, readable, and maintainable following industry best practices and AAA (Arrange-Act-Assert) pattern.

When to Use

Writing tests for new code
Improving test coverage
Establishing testing standards
Refactoring with test safety
Implementing TDD (Test-Driven Development)
Creating test utilities and mocks

Quick Start

Minimal working example:

// Jest/JavaScript example
describe("UserService", () => {
  describe("createUser", () => {
    it("should create user with valid data", async () => {
      // Arrange - Set up test data and dependencies
      const userData = {
        email: "john@example.com",
        firstName: "John",
        lastName: "Doe",
      };
      const mockDatabase = createMockDatabase();
      const service = new UserService(mockDatabase);

      // Act - Execute the function being tested
      const result = await service.createUser(userData);

SKILL.md on GitHub