Code coverage metrics in Software Engineering - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Code Coverage Types

Which type of code coverage measures whether each decision point (like an if statement) has been evaluated both true and false during testing?

A Branch coverage

B Statement coverage

C Function coverage

D Path coverage

💡 Hint

Think about coverage that checks all possible outcomes of decisions.

Branch coverage ensures that every possible branch (true and false) of decision points is tested. Statement coverage only checks if each line runs, function coverage checks if functions are called, and path coverage is more detailed, covering all possible paths.

📋 Factual

intermediate

Code Coverage Metric Calculation

If a program has 100 executable statements and a test suite executes 85 of them, what is the statement coverage percentage?

A 85%

B 15%

C 100%

D 75%

💡 Hint

Coverage percentage = (executed statements / total statements) * 100

Statement coverage is calculated by dividing the number of executed statements by the total statements, then multiplying by 100. Here, 85/100 * 100 = 85%.

🔍 Analysis

advanced

Interpreting Low Branch Coverage

A test suite shows 90% statement coverage but only 50% branch coverage. What does this most likely indicate about the tests?

A Tests are missing many functions and statements

B All functions are tested but some lines are not executed

C Tests cover all decision outcomes but miss some statements

D Most lines run but some decision outcomes are not tested

💡 Hint

Think about what branch coverage measures compared to statement coverage.

High statement coverage with low branch coverage means most lines run but some branches (true/false outcomes) of decisions are not tested. This can hide bugs in untested decision paths.

❓ Comparison

advanced

Comparing Path Coverage and Branch Coverage

Which statement best describes the difference between path coverage and branch coverage?

A Path coverage only tests function calls, branch coverage tests statements.

B Path coverage tests all possible sequences of branches, while branch coverage tests each branch once.

C Branch coverage tests all possible sequences of branches, while path coverage tests each branch once.

D Branch coverage measures code complexity, path coverage measures test duration.

💡 Hint

Consider how many combinations of branches each coverage type requires.

Path coverage requires testing every possible path through the code, which includes all combinations of branches. Branch coverage only requires each branch to be tested at least once, not all combinations.

❓ Reasoning

expert

Impact of 100% Statement Coverage on Software Quality

If a software project achieves 100% statement coverage but still has bugs, what is the most likely reason?

A The coverage tool is malfunctioning and reporting wrong results.

B The code has syntax errors that coverage tools cannot detect.

C Tests do not cover all possible input values and decision outcomes.

D 100% statement coverage guarantees no bugs exist.

💡 Hint

Think about what statement coverage measures and what it does not.

Statement coverage only ensures every line runs during tests but does not guarantee all logical paths or input cases are tested. Bugs can remain in untested decision outcomes or input scenarios.

Practice

1. What does code coverage primarily measure in software testing?

easy

A. The number of developers working on the code

B. The number of bugs found in the code

C. The speed of the test execution

D. The percentage of code executed by tests

Solution

1. Step 1: Understand the purpose of code coverage

   Code coverage shows how much of the program's code is run during testing.

2. Step 2: Identify what code coverage measures

   It measures the percentage of code lines or branches executed by tests, not bugs or speed.

3. Final Answer:

   The percentage of code executed by tests -> Option D

4. Quick Check:

   Code coverage = executed code percentage [OK]

Hint: Code coverage = how much code tests run [OK]

Common Mistakes:

• Confusing coverage with bug count
• Thinking coverage measures test speed
• Assuming coverage counts developers

2. Which of the following is a common type of code coverage metric?

easy

A. Branch coverage

B. Memory coverage

C. Network coverage

D. User coverage

Solution

1. Step 1: Recall common code coverage types

   Common types include line coverage, branch coverage, and function coverage.

2. Step 2: Identify valid coverage types

   Branch coverage measures if all decision branches are tested; memory, network, and user coverage are not standard metrics.

3. Final Answer:

   Branch coverage -> Option A

4. Quick Check:

   Branch coverage is a standard metric [OK]

Hint: Branch coverage is a standard metric name [OK]

Common Mistakes:

• Choosing non-existent coverage types
• Confusing coverage with unrelated terms
• Ignoring common coverage categories

3. Consider a program with 100 lines of code. A test suite runs 80 lines and covers all branches in those lines. What is the approximate line coverage percentage?

medium

A. 20%

B. 100%

C. 80%

D. 50%

Solution

1. Step 1: Calculate line coverage

   Line coverage = (lines executed / total lines) x 100 = (80 / 100) x 100.

2. Step 2: Compute the percentage

   80 divided by 100 equals 0.8, multiplied by 100 gives 80% coverage.

3. Final Answer:

   80% -> Option C

4. Quick Check:

   80/100 = 0.8 = 80% [OK]

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

Common Mistakes:

• Confusing branch coverage with line coverage
• Calculating 100% because all branches covered
• Mixing up executed and total lines

4. A developer reports 90% code coverage, but some bugs remain. What is the most likely reason?

medium

A. High coverage does not guarantee all bugs are found

B. The coverage tool is broken

C. Tests ran too slowly

D. Code coverage measures bug count

Solution

1. Step 1: Understand code coverage limits

   Code coverage shows tested code amount but does not ensure test quality or bug detection.

2. Step 2: Identify why bugs remain

   Even with 90% coverage, tests might miss edge cases or logic errors causing bugs.

3. Final Answer:

   High coverage does not guarantee all bugs are found -> Option A

4. Quick Check:

   Coverage ≠ bug-free code [OK]

Hint: Coverage shows tested code, not bug absence [OK]

Common Mistakes:

• Assuming coverage means no bugs
• Blaming coverage tools without evidence
• Confusing coverage with test speed

5. You want to improve your test suite to cover all decision branches in a function with multiple if-else statements. Which approach best increases branch coverage?

hard

A. Write tests that only check the function's return value

B. Write tests that execute both true and false paths of each condition

C. Run the existing tests multiple times

D. Add print statements inside the function

Solution

1. Step 1: Understand branch coverage goal

   Branch coverage requires testing all possible paths of decision points (true and false).

2. Step 2: Choose the best testing approach

   Writing tests that cover both true and false branches ensures all decision paths run during testing.

3. Final Answer:

   Write tests that execute both true and false paths of each condition -> Option B

4. Quick Check:

   Branch coverage = test all decision paths [OK]

Hint: Test both true and false branches for full coverage [OK]

Common Mistakes:

• Testing only return values misses branches
• Rerunning tests doesn't increase coverage
• Adding print statements doesn't affect coverage