Test coverage metrics in Testing Fundamentals - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is test coverage in software testing?

Test coverage measures how much of the software's code or features are tested by the test cases. It helps find untested parts.

beginner

Name two common types of test coverage metrics.

Two common types are code coverage (which checks how much code is tested) and requirement coverage (which checks how many requirements are tested).

intermediate

What does statement coverage measure?

Statement coverage measures the percentage of executable statements in the code that have been run by tests.

intermediate

Why is 100% test coverage not always enough?

Because tests might run code but not check if it works correctly. Also, some bugs happen in combinations or unexpected inputs not covered by tests.

intermediate

What is branch coverage and why is it important?

Branch coverage measures if every possible branch (like if-else branches) in the code has been tested. It helps find missing tests for decision points.

Which test coverage metric measures the percentage of code lines executed by tests?

A Requirement coverage

B Statement coverage

C Branch coverage

D Path coverage

Statement coverage counts how many code statements are run during testing.

What does requirement coverage focus on?

A Testing all functions

B Testing all code branches

C Testing all user requirements

D Testing all variables

Requirement coverage checks if all specified user needs are tested.

Why might 100% code coverage still miss bugs?

A Because code coverage only measures requirements

B Because code coverage tools are inaccurate

C Because tests run too slowly

D Because tests might not check outputs or logic correctness

Running code doesn't guarantee the test checks if the result is correct.

Branch coverage ensures testing of:

A All decision paths like if-else

B All user stories

C All code statements

D All database queries

Branch coverage tests every possible decision path in the code.

Which metric helps identify untested requirements?

A Requirement coverage

B Code coverage

C Branch coverage

D Statement coverage

Requirement coverage tracks which requirements have test cases.

Explain what test coverage metrics are and why they matter in software testing.

Think about how much of the software is tested.

Describe the difference between statement coverage and branch coverage.

One counts lines, the other counts decision points.

Practice

1. What does test coverage metric measure in software testing?

easy

A. The time taken to run all tests

B. The number of bugs found during testing

C. The percentage of code or features tested compared to total code or features

D. The number of testers involved in the project

Solution

1. Step 1: Understand the purpose of test coverage

   Test coverage measures how much of the software is tested, usually as a percentage.

2. Step 2: Identify what is compared in coverage

   It compares tested code or features against the total code or features available.

3. Final Answer:

   The percentage of code or features tested compared to total code or features -> Option C

4. Quick Check:

   Test coverage = tested items / total items [OK]

Hint: Coverage shows tested parts over total parts [OK]

Common Mistakes:

• Confusing coverage with number of bugs
• Thinking coverage measures test duration
• Assuming coverage counts testers

2. Which of the following is the correct formula for calculating test coverage percentage?

easy

A. (Number of tested code lines / Total code lines) * 100

B. (Total tests / Number of testers) * 100

C. (Number of bugs found / Total tests) * 100

D. (Number of tests run / Total number of tests) * 100

Solution

1. Step 1: Identify what test coverage measures

   Test coverage measures how much code is tested, so it relates to tested code lines over total code lines.

2. Step 2: Match formula to coverage concept

   The formula is (tested code lines / total code lines) * 100 to get percentage coverage.

3. Final Answer:

   (Number of tested code lines / Total code lines) * 100 -> Option A

4. Quick Check:

   Coverage % = tested lines / total lines * 100 [OK]

Hint: Coverage = tested code lines divided by total lines [OK]

Common Mistakes:

• Using number of tests run instead of code lines
• Confusing bugs found with coverage
• Dividing by number of testers

3. Consider a software module with 200 lines of code. If 150 lines are executed during testing, what is the test coverage percentage?

medium

A. 85%

B. 75%

C. 65%

D. 70%

Solution

1. Step 1: Identify total and tested lines

   Total lines = 200, tested lines = 150.

2. Step 2: Calculate coverage percentage

   Coverage = (150 / 200) * 100 = 0.75 * 100 = 75%.

3. Final Answer:

   75% -> Option B

4. Quick Check:

   150/200 = 0.75 = 75% [OK]

Hint: Divide tested lines by total lines, multiply by 100 [OK]

Common Mistakes:

• Dividing total lines by tested lines
• Forgetting to multiply by 100
• Mixing up tested and total lines

4. A tester reports 90% test coverage, but some critical code paths are not tested. What is the likely issue?

medium

A. Coverage metric only measures quantity, not quality of tests

B. Tester calculated coverage incorrectly

C. Test coverage always guarantees all paths tested

D. The software has no untested code

Solution

1. Step 1: Understand what coverage measures

   Coverage measures how much code is tested but not which specific paths or quality of tests.

2. Step 2: Identify why critical paths might be missed

   High coverage can still miss important paths if tests do not cover all scenarios.

3. Final Answer:

   Coverage metric only measures quantity, not quality of tests -> Option A

4. Quick Check:

   Coverage % ≠ test quality [OK]

Hint: Coverage shows quantity, not test quality [OK]

Common Mistakes:

• Assuming coverage means all paths tested
• Blaming tester calculation without proof
• Ignoring untested critical paths

5. You have a project with 3 modules: Module A (100 lines, 80 tested), Module B (150 lines, 120 tested), Module C (50 lines, 40 tested). What is the overall test coverage percentage?

hard

A. 70%

B. 75%

C. 77.5%

D. 80%

Solution

1. Step 1: Calculate total lines and total tested lines

   Total lines = 100 + 150 + 50 = 300 lines. Tested lines = 80 + 120 + 40 = 240 lines.

2. Step 2: Calculate overall coverage percentage

   Coverage = (240 / 300) * 100 = 80%.

3. Step 3: Recalculate carefully

   Sum tested lines: 80 + 120 + 40 = 240. Sum total lines: 100 + 150 + 50 = 300. Coverage = (240/300)*100 = 80%.

4. Final Answer:

   80% -> Option D

5. Quick Check:

   Total tested / total lines = 240/300 = 80% [OK]

Hint: Sum tested and total lines, then divide and multiply by 100 [OK]

Common Mistakes:

• Averaging percentages instead of totals
• Adding percentages directly
• Mixing tested and total lines