What is test coverage?
💡 Concept: Test Coverage
Test coverage measures the extent to which your source code is tested by automated tests.
📘 Quick Intro
It is a key metric to ensure your tests cover critical parts of the codebase.
🧠 Analogy
Like checking how many pages of a book have been proofread for errors.
🔧 Technical Explanation
- Measures percentage of code executed by tests.
- Common types: line coverage, branch coverage, path coverage.
- Tools: Visual Studio Coverage, Coverlet, dotCover.
- High coverage reduces chances of undetected bugs.
- Does not guarantee absence of bugs.
🎯 Use Cases
- ✅ Assessing test suite effectiveness.
- ✅ Identifying untested code.
- ✅ Improving software quality.
- ✅ Supporting continuous integration.
💻 Example Tools
// Run tests with coverage using Coverlet
dotnet test /p:CollectCoverage=true
dotnet reportgenerator -reports:coverage.cobertura.xml -targetdir:coveragereport
❓ Interview Q&A
Q1: What is test coverage?
A: The percentage of code tested by automated tests.
Q2: Name common types of coverage.
A: Line, branch, path.
Q3: Does high coverage guarantee bug-free code?
A: No.
Q4: What tools are used for coverage?
A: Coverlet, dotCover.
Q5: How to improve coverage?
A: Add tests for uncovered code.
Q6: What is branch coverage?
A: Coverage of conditional branches.
Q7: Is test coverage important?
A: Yes.
Q8: What is path coverage?
A: Coverage of all execution paths.
Q9: Can coverage tools slow builds?
A: Sometimes.
Q10: Should 100% coverage be a goal?
A: Not always necessary.
📝 MCQs
Q1. What is test coverage?
- Percentage of code tested
- Number of tests
- Lines of code
- Test duration
Q2. Name a coverage type.
- Line coverage
- Function coverage
- File coverage
- Module coverage
Q3. Does high coverage mean no bugs?
- Yes
- No
- Maybe
- Sometimes
Q4. Name a coverage tool.
- NUnit
- MSTest
- Coverlet
- Selenium
Q5. How to improve coverage?
- Remove code
- Add tests
- Ignore code
- Use comments
Q6. What is branch coverage?
- Conditional branches
- Function calls
- Files
- Modules
Q7. Is coverage important?
- No
- Yes
- Sometimes
- Rarely
Q8. What is path coverage?
- All execution paths
- Lines
- Branches
- Functions
Q9. Can coverage slow builds?
- Always
- Sometimes
- Never
- Rarely
Q10. Should 100% coverage be goal?
- Always
- Never
- Not always
- Sometimes
💡 Bonus Insight
Test coverage is a helpful metric but should be balanced with meaningful tests for true quality.
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