Unit Testing
Unit Testing is the testing of individual components or units of code (such as functions, methods, or classes) to verify that they work as intended in isolation.
From a manual tester’s perspective, unit testing is primarily a developer activity, but understanding it is essential.
1. Definition
Unit Testing is the testing of individual components or units of code (such as functions, methods, or classes) to verify that they work as intended in isolation.
From a manual tester’s perspective, unit testing is primarily a developer activity, but understanding it is essential.
2. Purpose of Unit Testing
- Validate correctness of individual units
- Detect defects early in development
- Prevent defect propagation to higher levels
- Improve code quality and design
3. Who Performs Unit Testing
- Primarily developers
-
Manual testers usually do not execute unit tests, but:
- Review unit test results
- Understand unit-level failures
- Collaborate with developers
4. What Is Considered a Unit
- A function or method
- A class
- A module (smallest testable part of the system)
5. Characteristics of Unit Testing
- Focused on internal logic
- Tests run in isolation
- Fast execution
- Covers positive and negative scenarios
6. Manual Tester’s Role in Unit Testing (Conceptual)
Manual testers:
- Understand what has been unit tested
- Identify gaps in unit test coverage
- Ensure unit-tested features are ready for integration testing
- Avoid duplicating unit tests at system level
7. Unit Testing vs System Testing
| Aspect | Unit Testing | System Testing |
|---|---|---|
| Scope | Single component | Entire application |
| Performed by | Developers | Testers |
| Environment | Development | Test environment |
| Focus | Code correctness | Business behavior |
8. Why Manual Testers Must Understand Unit Testing
- Helps identify root cause of defects
- Prevents invalid defect reporting
- Improves collaboration with developers
- Clarifies responsibility boundaries
9. Common Misconceptions
- Unit testing replaces system testing ❌
- Testers don’t need to know unit testing ❌
- Passing unit tests means feature is bug-free ❌
10. Real-Time Example
If a calculation method is unit tested:
- Tester focuses on integration and business rules
- Avoids re-testing internal logic unnecessarily
11. Interview-Ready Answers
Short answer:
Unit testing is the testing of individual code components to ensure they work correctly in isolation.
Manual tester version:
Unit testing is mainly done by developers, but testers should understand it to ensure proper test coverage and avoid duplication.
12. Key Takeaway
Manual testers don’t execute unit tests, but must understand unit testing to test smarter at higher levels.