Testing Module

Welcome to the Testing Module! Testing is one of the most critical skills for a junior developer to move from “writing code that works” to “building professional software.”

In this module, you’ll learn how to write tests that catch bugs before they reach production, how to design code that is easy to test, and how to use testing as a powerful debugging tool.

Learning Path

1. What is Testing? - Basic definition and mental model.
2. Why Testing Matters - Business value and preventing production disasters.
3. Types of Testing - Unit, Integration, E2E (the testing pyramid).
4. Unit Testing - Deep dive into unit tests with Python/Java examples.
5. Integration Testing - Testing how components work together.
6. Manual vs. Automated Testing - Pros/cons and when to use each.
7. Writing Testable Code - Dependency injection and clean code for tests.
8. Debugging with Tests - Using tests to reproduce and fix bugs.
9. Test-Driven Development - Red-Green-Refactor cycle.
10. Testing APIs - Mocking requests and validating JSON responses.
11. Testing Databases - Using test databases and cleanup.
12. Common Testing Mistakes - Testing implementation details, fragile tests, etc.

Ready to Start?

Jump into the first lesson: What is Testing?