Test-First Development Skill

Test-First Development (TDD) ensures that code is written to satisfy specific, predefined requirements, leading to higher quality and better design.

TDD Workflow

1. Red: Write a failing test for a small piece of functionality.
2. Green: Write the minimum amount of code required to make the test pass.
3. Refactor: Clean up the code while ensuring the tests remain green.

Test Design Principles

1. Comprehensive Coverage

• Normal Cases: Test the expected "happy path" behavior.
• Boundary Values: Test inputs at the edges of valid ranges (e.g., 0, max_int, empty strings).
• Edge Cases: Test unusual or extreme conditions (e.g., network timeout, disk full, null values).
• Error Handling: Verify that the system fails gracefully and returns appropriate error messages.

2. Structure (Arrange-Act-Assert)

Follow the AAA pattern for clear and maintainable tests:

• Arrange: Set up the necessary preconditions and inputs.
• Act: Execute the function or method being tested.
• Assert: Verify that the outcome matches the expectation.

Best Practices

• One Assertion per Test: Aim to test a single concept per test case.
• Descriptive Naming: Name tests clearly (e.g., test_should_reject_invalid_api_key).
• Independence: Ensure tests do not depend on each other or on a specific execution order.
• Fast Execution: Keep unit tests fast to encourage frequent execution.