Branch Testing is a technique in software testing that ensures all control flow branches in a program are tested. These branches include both conditional (e.g., if-else) and unconditional paths (e.g., sequential execution).

Key Concepts

1. Branch Coverage Formula:
   Branch Coverage (%) = (Number of Executed Branches / Total Branches) × 100
2. Objectives:

• Ensure each decision point (e.g., if, switch, loops) evaluates to all possible outcomes at least once.
• Validate both true and false outcomes for conditional branches.

3. 100% Branch Coverage:

• Ensures all branches are executed by test cases.
• Guarantees 100% statement coverage (but not the other way around).

Benefits of Branch Testing

• Detects missing branches or conditions.
• Provides better control flow testing than statement coverage.
• Improves reliability of code by covering all decision outcomes.

Limitations

• Does not test specific paths or combinations of branches.
• May still miss defects that depend on a sequence of branch executions.

Example

Consider the following code:

if (x > 0):  
    print("Positive")  
else:  
    print("Non-positive")  
print("Done")

Branches:

1. if (x > 0) → True
2. if (x > 0) → False

Test Cases for 100% Branch Coverage:

• Test Case 1: x = 5 → True branch executed.
• Test Case 2: x = -3 → False branch executed.

Result: Both branches are tested, achieving 100% branch coverage.

Main idea:

Branch testing is essential for ensuring code correctness, especially in decision-heavy logic. By subsuming statement coverage, it offers more robust test coverage.

Here are ISTQB-style multiple-choice questions (MCQs) on Branch Testing and Branch Coverage:

1. What is the primary goal of branch testing?

a) To execute all statements in the code
b) To execute all decision outcomes in the code
c) To execute all paths in the code
d) To execute all combinations of conditions

Answer: b) To execute all decision outcomes in the code

2. What is the formula for branch coverage?

a) (Number of executed branches / Total branches) × 100
b) (Number of executed statements / Total statements) × 100
c) (Number of executed paths / Total paths) × 100
d) (Number of executed conditions / Total conditions) × 100

Answer: a) (Number of executed branches / Total branches) × 100

3. Which of the following is true about 100% branch coverage?

a) It guarantees all paths in the code are tested.
b) It ensures 100% statement coverage.
c) It detects all possible defects in the code.
d) It guarantees all combinations of inputs are tested.

Answer: b) It ensures 100% statement coverage.

4. In the following code snippet, how many branches need to be tested to achieve 100% branch coverage?

if (x > 0):  
    print("Positive")  
else:  
    print("Non-positive")  
print("Done")

a) 1
b) 2
c) 3
d) 4

Answer: b) 2

5. Which of the following is NOT tested by 100% branch coverage?

a) All decision outcomes
b) All branches in the code
c) All sequential statements
d) All possible paths through the code

Answer: d) All possible paths through the code

6. What type of branches are tested in branch testing?

a) Conditional branches only
b) Unconditional branches only
c) Both conditional and unconditional branches
d) Only branches with loops

Answer: c) Both conditional and unconditional branches

7. How does branch coverage compare to statement coverage?

a) Branch coverage subsumes statement coverage.
b) Statement coverage subsumes branch coverage.
c) They are equivalent.
d) They measure the same aspect of testing.

Answer: a) Branch coverage subsumes statement coverage.

8. What type of defect might 100% branch coverage fail to detect?

a) Missing statements
b) Dead code
c) Defects in a specific path
d) Incorrect decision logic

Answer: c) Defects in a specific path

9. What does achieving 100% branch coverage imply about statement coverage?

a) Statement coverage will always be less than branch coverage.
b) Statement coverage will always be equal to branch coverage.
c) 100% statement coverage is guaranteed.
d) Statement coverage is irrelevant.

Answer: c) 100% statement coverage is guaranteed.

10. Which of the following is required to achieve 100% branch coverage for a loop?

a) Testing the loop condition for true only
b) Testing the loop condition for false only
c) Testing the loop condition for both true and false outcomes
d) Executing the loop multiple times

Answer: c) Testing the loop condition for both true and false outcomes