webapp-testing

name	webapp-testing
description	Guide for writing tests: unit tests, integration tests, and end-to-end testing strategies

Testing

Instructions

When the user asks you to write tests, test a feature, or set up testing:

1. Choose the right test level:

   • Unit tests — test individual functions/classes in isolation
   • Integration tests — test module interactions
   • E2E tests — test full user workflows

2. Test structure — follow Arrange-Act-Assert (AAA) pattern:

   test('description', () => {
     // Arrange — set up test data
     // Act — call the function under test
     // Assert — check the result
   });
   

3. Test naming — use descriptive names: "should return empty array when input is empty"

Unit Testing Best Practices

• Test one behavior per test
• Use descriptive assertion messages
• Test edge cases: empty inputs, null/undefined, boundary values
• Test error cases: invalid input, thrown exceptions
• Avoid testing implementation details — test behavior

Mocking

• Mock external dependencies (APIs, databases, file system)
• Use minimal mocks — only mock what you need
• Verify mock calls when the interaction IS the behavior

Testing Frameworks

• Node.js built-in: node:test with node:assert
• Vitest: fast, Vite-compatible, ESM native
• Jest: mature ecosystem, good for React
• Playwright: browser E2E testing