White-box testing techniques in Software Engineering - Mini Project: Build & Apply

White-box Testing Techniques

📖 Scenario: You are part of a software development team. Your team wants to improve the quality of the code by testing it thoroughly. You will learn how to apply white-box testing techniques to check the internal workings of a simple function.

🎯 Goal: Build a step-by-step understanding of white-box testing techniques by creating a simple function, setting up test conditions, applying a white-box testing method, and completing the test coverage.

📋 What You'll Learn

Create a simple function with conditional logic

Define a variable to track test coverage

Apply a white-box testing technique (e.g., statement coverage)

Complete the test setup to ensure all paths are tested

💡 Why This Matters

🌍 Real World

White-box testing helps developers find bugs by checking the internal logic of their code. It ensures all parts of the code work as expected.

💼 Career

Software testers and developers use white-box testing techniques to improve software quality and reliability before release.

1

Create a simple function with conditional logic

Write a Python function called check_number that takes one parameter num. The function should return the string 'Positive' if num is greater than zero, 'Zero' if num is zero, and 'Negative' if num is less than zero.

Software Engineering

# Your code here

Hint

Use if, elif, and else statements to check the value of num.

2

Define a variable to track test coverage

Create a variable called coverage and set it to an empty list. This list will store the names of the branches tested in the function.

Software Engineering

def check_number(num):
    if num > 0:
        return 'Positive'
    elif num == 0:
        return 'Zero'
    else:
        return 'Negative'

# Your code here

Hint

Use an empty list [] to start tracking coverage.

3

Apply a white-box testing technique (statement coverage)

Write three lines of code that call check_number with the values 5, 0, and -3. After each call, append the string 'Positive', 'Zero', or 'Negative' respectively to the coverage list to track which branches have been tested.

Software Engineering

def check_number(num):
    if num > 0:
        return 'Positive'
    elif num == 0:
        return 'Zero'
    else:
        return 'Negative'

coverage = []
# Your code here

Hint

Call the function with each test value and append the result to coverage.

4

Complete the test setup to ensure all paths are tested

Add a line of code that creates a set called tested_branches from the coverage list to show unique branches tested. This helps confirm all branches in the function have been covered.

Software Engineering

def check_number(num):
    if num > 0:
        return 'Positive'
    elif num == 0:
        return 'Zero'
    else:
        return 'Negative'

coverage = []
coverage.append(check_number(5))
coverage.append(check_number(0))
coverage.append(check_number(-3))
# Your code here

Hint

Use the set() function to get unique tested branches.

Practice

1. Which of the following best describes white-box testing?

easy

A. Testing that examines the internal structure of the code

B. Testing that focuses only on user interface behavior

C. Testing done without knowledge of the code

D. Testing that only checks software performance

Solution

1. Step 1: Understand white-box testing definition

   White-box testing involves looking inside the code to test its logic and structure.

2. Step 2: Compare options to definition

   Testing that examines the internal structure of the code matches this definition exactly, while others focus on external or unrelated aspects.

3. Final Answer:

   Testing that examines the internal structure of the code -> Option A

4. Quick Check:

   White-box testing = internal code check [OK]

Hint: White-box tests look inside the code, not just outside [OK]

Common Mistakes:

• Confusing white-box with black-box testing
• Thinking white-box tests only check UI
• Assuming white-box ignores code structure

2. Which syntax correctly represents a common white-box testing technique?

easy

A. User acceptance testing

B. Branch coverage

C. Load testing

D. Smoke testing

Solution

1. Step 1: Identify white-box testing techniques

   Common white-box techniques include statement, branch, path, and condition coverage.

2. Step 2: Match options to white-box techniques

   Only branch coverage is a white-box technique; others are types of testing but not white-box.

3. Final Answer:

   Branch coverage -> Option B

4. Quick Check:

   Branch coverage = white-box technique [OK]

Hint: Branch coverage is a classic white-box technique [OK]

Common Mistakes:

• Confusing black-box tests with white-box
• Choosing performance or acceptance tests
• Ignoring coverage-based techniques

3. Consider the following code snippet:

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

Which white-box testing technique ensures both if and else branches are tested?

medium

A. Statement coverage

B. Path coverage

C. Branch coverage

D. Condition coverage

Solution

1. Step 1: Understand the code branches

   The code has two branches: one for x > 0 true, one for false.

2. Step 2: Identify technique testing all branches

   Branch coverage requires testing each branch (if and else) at least once.

3. Final Answer:

   Branch coverage -> Option C

4. Quick Check:

   Branch coverage = test all branches [OK]

Hint: Branch coverage tests all decision paths [OK]

Common Mistakes:

• Confusing statement coverage with branch coverage
• Thinking path coverage is simpler
• Ignoring else branch testing

4. A tester wrote this code to check condition coverage:

if (a > 10 && b < 5) {
  print("Valid");
}

Which mistake would cause incomplete condition coverage?

medium

A. Testing only when both conditions are true

B. Testing when a is 5 and b is 3

C. Testing when a is 15 and b is 6

D. Testing when a is 20 and b is 2

Solution

1. Step 1: Understand condition coverage

   Condition coverage requires testing each condition (a > 10 and b < 5) as true and false separately.

2. Step 2: Analyze testing only both true

   If only tested when both are true, false cases for each condition are not tested, so coverage is incomplete.

3. Final Answer:

   Testing only when both conditions are true -> Option A

4. Quick Check:

   Condition coverage = test each condition true/false [OK]

Hint: Test each condition true and false separately [OK]

Common Mistakes:

• Testing only combined true cases
• Ignoring false condition tests
• Assuming one test covers all conditions

5. You want to ensure every possible route through this code is tested:

if (x > 0) {
  if (y > 0) {
    print("Both positive");
  } else {
    print("x positive, y non-positive");
  }
} else {
  print("x non-positive");
}

Which white-box testing technique best guarantees this?

hard

A. Condition coverage

B. Statement coverage

C. Branch coverage

D. Path coverage

Solution

1. Step 1: Identify all possible paths

   There are three paths: both x and y positive, x positive and y non-positive, x non-positive.

2. Step 2: Understand path coverage

   Path coverage requires testing every possible route through the code, covering all combinations of decisions.

3. Step 3: Compare with other techniques

   Statement and branch coverage do not guarantee all paths; condition coverage tests conditions but not all paths.

4. Final Answer:

   Path coverage -> Option D

5. Quick Check:

   Path coverage = test all routes [OK]

Hint: Path coverage tests every possible route through code [OK]

Common Mistakes:

• Confusing branch with path coverage
• Assuming statement coverage is enough
• Ignoring nested conditions