Branch coverage in Testing Fundamentals - Test Execution Trace

Test Overview

This test checks if all possible branches (true and false paths) in a simple decision are executed. It verifies that the code correctly handles both conditions.

Test Code - PyTest

Testing Fundamentals

def is_even(num):
    if num % 2 == 0:
        return True
    else:
        return False


def test_is_even():
    assert is_even(4) == True  # Tests the 'true' branch
    assert is_even(5) == False # Tests the 'false' branch

if __name__ == '__main__':
    test_is_even()

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	Test environment is ready with the is_even function loaded	—	PASS
2	Calls is_even(4)	Function receives input 4	Checks if 4 % 2 == 0 evaluates to True	PASS
3	Returns True for input 4	Function returns True	Assert that returned value is True	PASS
4	Calls is_even(5)	Function receives input 5	Checks if 5 % 2 == 0 evaluates to False	PASS
5	Returns False for input 5	Function returns False	Assert that returned value is False	PASS
6	Test ends	All assertions passed, both branches covered	Branch coverage achieved for both true and false paths	PASS

Failure Scenario

Failing Condition: If the function always returns True or always returns False, missing one branch

Execution Trace Quiz - 3 Questions

What does branch coverage ensure in this test?

A Only the false path of the if statement is tested

B Only the true path of the if statement is tested

C Both true and false paths of the if statement are tested

D The function is tested with random inputs

Key Result

Branch coverage testing ensures that every possible decision path in the code is executed at least once, helping catch errors in all conditions.

Practice

1. What does branch coverage testing ensure in software testing?

easy

A. All possible paths of each decision point are tested

B. Only the main function is tested

C. All variables are initialized

D. The software runs faster

Solution

1. Step 1: Understand branch coverage concept

   Branch coverage means testing every decision point in the code, including both true and false outcomes.

2. Step 2: Match concept to options

   All possible paths of each decision point are tested correctly states that all possible paths of each decision point are tested, which is the essence of branch coverage.

3. Final Answer:

   All possible paths of each decision point are tested -> Option A

4. Quick Check:

   Branch coverage = all decision paths tested [OK]

Hint: Branch coverage tests both true and false paths [OK]

Common Mistakes:

• Confusing branch coverage with statement coverage
• Thinking it only tests main functions
• Assuming it improves speed

2. Which of the following is the correct way to write a branch coverage test condition in pseudocode?

easy

A. print('Test complete')

B. while x > 10 do A

C. for i in range(10): do A

D. if (x > 10) then do A else do B

Solution

1. Step 1: Identify branch decision structure

   Branch coverage requires a decision point with two or more paths, like an if-else condition.

2. Step 2: Check options for decision points

   if (x > 10) then do A else do B shows an if-else statement, which has two branches (true and false). Other options do not have decision branches.

3. Final Answer:

   if (x > 10) then do A else do B -> Option D

4. Quick Check:

   If-else = branch decision [OK]

Hint: Look for if-else to identify branches [OK]

Common Mistakes:

• Choosing loops as branch examples
• Ignoring else part of if-else
• Confusing print statements with branches

3. Consider the following code snippet:

if (a > 0) {
  if (b == 5) {
    print('Path 1');
  } else {
    print('Path 2');
  }
} else {
  print('Path 3');
}

How many test cases are needed for 100% branch coverage?

medium

A. 3

B. 4

C. 2

D. 5

Solution

1. Step 1: Identify decision points and branches

   There are two if statements: outer (a > 0) with true/false branches, inner (b == 5) with true/false branches.

2. Step 2: Count unique branches

   Outer if: 2 branches (true, false). Inner if (only if outer true): 2 branches. Total branches = 3 unique paths: Path 1, Path 2, Path 3.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Branches = 3 paths [OK]

Hint: Count all true/false branches in nested ifs [OK]

Common Mistakes:

• Counting only outer if branches
• Assuming each if adds 2 test cases independently
• Ignoring nested structure

4. You have this code:

if (x != 0) {
  print('Non-zero');
}

A test case with x = 0 is missing. What branch coverage issue does this cause?

medium

A. True branch not tested

B. False branch not tested

C. Syntax error in code

D. All branches covered

Solution

1. Step 1: Identify branches in the if condition

   The if condition has two branches: true (x != 0) and false (x == 0).

2. Step 2: Analyze test cases given

   Only test cases with x != 0 exist, so true branch is tested but false branch (x == 0) is missing.

3. Final Answer:

   False branch not tested -> Option B

4. Quick Check:

   Missing false branch test = coverage gap [OK]

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

Common Mistakes:

• Assuming one test case covers all branches
• Confusing true and false branches
• Thinking missing test causes syntax error

5. Given this code:

if (score >= 90) {
  grade = 'A';
} else if (score >= 75) {
  grade = 'B';
} else {
  grade = 'C';
}

How many test cases are needed for 100% branch coverage?

hard

A. 2

B. 5

C. 3

D. 4

Solution

1. Step 1: Identify all decision points and branches

   There are two if conditions: first (score >= 90) with true/false branches, second (score >= 75) with true/false branches inside else.

2. Step 2: Count unique branches

   Branches: first if true (score>=90), first false + second true (75<=score<90), first false + second false (score<75). Total 3 test cases needed for 100% coverage.

3. Final Answer:

   3 -> Option C

4. Quick Check:

   if-else-if-else chain = 3 test cases [OK]

Hint: Count all true/false branches in if-else if-else chains [OK]

Common Mistakes:

• Counting only if statements, ignoring else
• Assuming 4 test cases are needed
• Missing nested else if branches