What is test coverage?
💡 Concept: Test Coverage
Test coverage measures the extent to which your source code is tested by automated tests, helping ensure software quality.
📘 Quick Intro
It quantifies the percentage of code executed during tests, highlighting untested parts and guiding improvements.
🧠 Analogy
Think of test coverage like inspecting every room in a house before buying it, ensuring no hidden problems.
🔧 Technical Explanation
- 📊 Code coverage tools analyze which lines and branches are executed during tests.
- 🧩 Common metrics include line coverage, branch coverage, and method coverage.
- 🛠️ High coverage improves confidence but doesn’t guarantee bug-free code.
- ⚠️ 100% coverage is ideal but not always practical.
- 🔄 Continuous integration can automate coverage checks.
🎯 Use Cases
- ✅ Identifying untested code areas.
- ✅ Improving automated test suites.
- ✅ Supporting refactoring with confidence.
- ✅ Enforcing quality standards.
💻 Code Example
// This is a conceptual example; use tools like Visual Studio or dotCover for coverage analysis
public class Calculator {
public int Add(int a, int b) {
return a + b;
}
}
❓ Interview Q&A
Q1: What is test coverage?
A: The percentage of code tested by automated tests.
Q2: Does 100% coverage mean no bugs?
A: No, it only shows code was executed during tests.
Q3: Name common coverage metrics.
A: Line, branch, method coverage.
Q4: Can test coverage be automated?
A: Yes, using CI tools.
Q5: What tools analyze coverage in C#?
A: Visual Studio, dotCover, OpenCover.
Q6: Should tests cover all code?
A: Aim for critical paths primarily.
Q7: What is branch coverage?
A: Percentage of branches tested in conditionals.
Q8: How does coverage help developers?
A: It highlights untested code.
Q9: Can high coverage replace good tests?
A: No, tests must be meaningful.
Q10: How is coverage reported?
A: Through reports and dashboards.
📝 MCQs
Q1. What is test coverage?
- Percentage of code tested
- Lines of code
- Number of tests
- Bugs found
Q2. Does 100% coverage mean no bugs?
- Yes
- No
- Sometimes
- Always
Q3. Common coverage metrics?
- Line, branch, method
- Class, object, method
- Variables, constants, methods
- None
Q4. Can coverage be automated?
- No
- Yes
- Sometimes
- Never
Q5. Tools for coverage analysis?
- Visual Studio, dotCover
- Notepad
- Excel
- Git
Q6. Should tests cover all code?
- All code
- Critical paths
- Only UI
- Only backend
Q7. What is branch coverage?
- Branches in conditionals
- Branches in trees
- Branches in logs
- Branches in codebase
Q8. How coverage helps developers?
- Slows development
- Highlights untested code
- Creates bugs
- None
Q9. Can high coverage replace good tests?
- Yes
- No
- Sometimes
- Always
Q10. How is coverage reported?
- Logs
- Reports and dashboards
- Emails
- Alerts
💡 Bonus Insight
Test coverage is a valuable metric but must be combined with quality tests to ensure software reliability.
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