Branch coverage in Testing Fundamentals - Build an Automation Script

Test branch coverage for a simple function

Preconditions (2)

Step 1: Call the function with a value that makes the if condition true

Step 2: Verify the function returns the expected result for the true branch

Step 3: Call the function with a value that makes the if condition false

Step 4: Verify the function returns the expected result for the false branch

✅ Expected Result: Both branches of the function are executed and verified, ensuring full branch coverage

Automation Requirements - pytest

Assertions Needed:

Assert the function returns correct output for true branch input

Assert the function returns correct output for false branch input

Best Practices:

Use clear and descriptive test function names

Test each branch separately to ensure coverage

Keep tests independent and repeatable

Automated Solution

Testing Fundamentals

def is_positive(number: int) -> str:
    if number > 0:
        return "Positive"
    else:
        return "Non-positive"

import pytest

def test_is_positive_true_branch():
    result = is_positive(5)
    assert result == "Positive"

def test_is_positive_false_branch():
    result = is_positive(0)
    assert result == "Non-positive"
    result = is_positive(-3)
    assert result == "Non-positive"

The function is_positive has two branches: one for numbers greater than zero, and one for zero or less.

The first test test_is_positive_true_branch calls the function with a positive number to cover the true branch and asserts the output is "Positive".

The second test test_is_positive_false_branch calls the function with zero and a negative number to cover the false branch and asserts the output is "Non-positive".

This way, both branches are executed and verified, achieving full branch coverage.

Common Mistakes - 3 Pitfalls

Testing only one branch of the if-else statement

Using the same input value for all tests

Not using assertions to verify output

Bonus Challenge

Now add data-driven testing with 3 different inputs to cover branches

Show Hint

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