Statement coverage in Testing Fundamentals - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is statement coverage in software testing?

Statement coverage measures the percentage of executable statements in the code that have been run by the test cases. It helps ensure that every line of code is tested at least once.

beginner

Why is statement coverage important?

It helps find parts of the code that are never executed during testing, which might hide bugs. Testing all statements increases confidence that the code works as expected.

beginner

How do you calculate statement coverage?

Statement coverage = (Number of statements executed by tests / Total number of statements) × 100%. For example, if 80 out of 100 statements run, coverage is 80%.

intermediate

Does 100% statement coverage guarantee bug-free software?

No. It means every statement ran, but it doesn't check if all conditions or paths work correctly. Other coverage types like branch coverage are needed for deeper testing.

beginner

Give a simple example of statement coverage.

If a function has 5 lines and your test runs 4 of them, statement coverage is 80%. For example, if an if-statement's else part never runs, those lines are not covered.

What does statement coverage measure?

A Number of test cases written

B Number of bugs found in the code

C Percentage of code statements executed by tests

D Time taken to run all tests

Statement coverage measures how many code statements are executed during testing.

If a program has 50 statements and tests run 40, what is the statement coverage?

A 80%

B 50%

C 40%

D 90%

Coverage = (40/50)*100 = 80%.

Does 100% statement coverage mean all bugs are found?

A Yes, all bugs are found

B Only syntax bugs are found

C Only performance bugs are found

D No, some bugs may still exist

100% statement coverage means all lines ran, but some bugs can still hide in logic or conditions.

Which coverage type is deeper than statement coverage?

A Syntax coverage

B Branch coverage

C Code style coverage

D Test case coverage

Branch coverage tests all possible paths, including if-else branches, which is deeper than statement coverage.

What happens if some code statements are never executed during testing?

A Those parts might contain hidden bugs

B The code is guaranteed bug-free

C Tests are faster

D Code is optimized automatically

Unexecuted code might hide bugs because it was never tested.

Explain statement coverage and why it is useful in software testing.

Think about how running each line of code helps find bugs.

Describe the limitations of statement coverage and what other coverage types can complement it.

Consider what happens if only some paths run but not others.

Practice

1. What does statement coverage measure in software testing?

easy

A. The number of test cases written

B. The number of bugs found in the code

C. The time taken to run all tests

D. The percentage of code lines executed during testing

Solution

1. Step 1: Understand the definition of statement coverage

   Statement coverage measures how many lines of code are executed when tests run.

2. Step 2: Compare options to the definition

   Only The percentage of code lines executed during testing correctly describes statement coverage as the percentage of executed code lines.

3. Final Answer:

   The percentage of code lines executed during testing -> Option D

4. Quick Check:

   Statement coverage = executed code lines percentage [OK]

Hint: Statement coverage counts executed lines, not tests or bugs [OK]

Common Mistakes:

• Confusing statement coverage with number of test cases
• Thinking it measures bugs found
• Mixing it up with test execution time

2. Which of the following is the correct way to describe statement coverage in a test report?

easy

A. Statement coverage is the number of test cases executed.

B. Statement coverage is the percentage of code statements executed during testing.

C. Statement coverage is the total time taken to run all tests.

D. Statement coverage is the number of bugs found per test.

Solution

1. Step 1: Identify the correct definition for statement coverage in reports

   Statement coverage is reported as the percentage of code statements executed during tests.

2. Step 2: Match options to the correct definition

   Statement coverage is the percentage of code statements executed during testing. correctly states this; others confuse coverage with test count, time, or bugs.

3. Final Answer:

   Statement coverage is the percentage of code statements executed during testing. -> Option B

4. Quick Check:

   Statement coverage = % of executed statements [OK]

Hint: Coverage means percent of executed code lines, not test counts [OK]

Common Mistakes:

• Reporting coverage as number of tests
• Confusing coverage with test duration
• Mixing coverage with bug counts

3. Consider this code snippet:

if (x > 0) {
  print("Positive");
} else {
  print("Non-positive");
}

If a test runs with x = 5, what is the statement coverage?

medium

A. 100% because all lines run

B. 75% because some lines run

C. 50% because only the if block runs

D. 0% because no else block runs

Solution

1. Step 1: Count total statements in the code

   There are 4 statements: the if condition, print("Positive"), else, print("Non-positive").

2. Step 2: Identify executed statements when x=5

   The if condition and print("Positive") run; else and its print do not run. So 2 out of 4 statements run.

3. Final Answer:

   50% because only the if block runs -> Option C

4. Quick Check:

   Executed statements = 2/4 = 50% [OK]

Hint: Only executed lines count; else block skipped means less coverage [OK]

Common Mistakes:

• Assuming else block runs anyway
• Counting conditions as multiple statements
• Thinking coverage is always 100%

4. You have this code:

if (a == 10) {
  print("Ten");
}
print("Done");

A test runs with a = 5 but reports 100% statement coverage. What is wrong?

medium

A. The test did not execute the if block, so coverage cannot be 100%

B. The print("Done") statement was not executed

C. The test input is invalid

D. The coverage tool counts only executed lines, so 100% is correct

Solution

1. Step 1: Identify statements and their execution

   There are 3 statements: if condition, print("Ten"), and print("Done"). With a=5, the if block is skipped, so print("Ten") is not executed.

2. Step 2: Check coverage report validity

   Since one statement is not executed, coverage cannot be 100%. The report is incorrect or the test did not run as expected.

3. Final Answer:

   The test did not execute the if block, so coverage cannot be 100% -> Option A

4. Quick Check:

   Skipped statements mean coverage less than 100% [OK]

Hint: Skipped code means coverage less than 100%, check test inputs [OK]

Common Mistakes:

• Assuming coverage counts unexecuted lines
• Ignoring skipped if blocks
• Trusting coverage tool blindly

5. Given this code:

if (score >= 90) {
  grade = 'A';
} else if (score >= 80) {
  grade = 'B';
} else {
  grade = 'C';
}

Which test inputs will achieve 100% statement coverage?

hard

A. score = 95, score = 85, and score = 70

B. score = 95 and score = 85

C. score = 95 only

D. score = 70 only

Solution

1. Step 1: Identify all statements in the code

   There are 7 statements: 3 conditions and 4 assignments (grade = 'A', grade = 'B', grade = 'C', plus else blocks).

2. Step 2: Determine inputs to cover all branches

   To cover all statements, tests must run each branch: score=95 covers first if, score=85 covers else if, score=70 covers else.

3. Final Answer:

   score = 95, score = 85, and score = 70 -> Option A

4. Quick Check:

   All branches covered by three inputs = 100% coverage [OK]

Hint: Test all branches to cover all statements fully [OK]

Common Mistakes:

• Testing only some branches
• Assuming one input covers all
• Ignoring else branch coverage