White Box Testing

Imagine you’re a car mechanic instead of just a test driver. Now you’re not just checking if the car runs — you’re looking at every single part of the engine, every wire, and every connection. That’s white box testing in software: you’re checking the actual code, not just what it does.

What Makes White Box Testing Special?

Code Coverage

• Input: Test each line of code
• Goal: Make sure every path through the code works
• Result: Nothing gets missed

Testing Paths: Let’s Take a Simple Login Function

Here’s a sample login function in Python:

def check_login(username, password):
    if username == "":
        return "Username empty"
    if password == "":
        return "Password empty"
    if validate_credentials(username, password):
        return "Login successful"
    return "Login failed"

With white box testing, you’d test:

• Empty username
• Empty password
• Valid credentials
• Invalid credentials

Every single path gets tested!

Real-World Example: Payment Processing System

With white box testing, you’re checking:

• How the code validates the card number
• Where the transaction data gets stored
• How the system handles declined payments
• Every possible path the code might take

The Power of White Box Testing

White box testing:

• Finds hidden bugs early
• Improves code quality
• Catches security issues
• Makes sure all code paths work

Why It Matters

White box testing complements black box testing. While black box testing ensures the software works for users, white box testing makes sure it’s built right from the inside out.

Testing Tips

• Start with understanding the code
• Map out all possible paths
• Test edge cases and boundary conditions
• Check error handling
• Verify security measures

It might seem more complex than black box testing, but that’s because you’re diving deep into the code’s inner workings. Think of it as being both the mechanic and the test driver — you know how it works and how it should perform!