Introduction

In this tutorial, we will demystify the concept of White Box Testing. Often known as Clear, Glass, or Structural testing, White Box Testing is a method where we test the internal structures or workings of an application, as opposed to its functionality, which is checked in Black Box Testing.

You will learn about the basic concepts of White Box Testing, its techniques, advantages, and how to implement it practically in your software testing process.

Prerequisites: Basic understanding of software development and testing is recommended.

Step-by-Step Guide

Understanding White Box Testing

White Box Testing involves testing the internal structures or workings of an application. It's performed by developers who write tests for their code to make sure their code works as expected.

In White Box Testing, the tester has to know how the system is implemented, its internal workings, which differentiates it from Black Box Testing.

White Box Testing Techniques

There are several techniques for performing White Box Testing:

1. Statement Coverage: This ensures that every statement in the code is executed at least once.
2. Decision Coverage: This ensures that every decision (true/false) in the code is executed at least once.
3. Path Coverage: This ensures that all paths in the flow control graph are traversed at least once.

Advantages of White Box Testing

1. Thoroughness: Since it involves testing the internal structure of the application, it's more thorough.
2. Early Bug Detection: It can help detect bugs early in the development phase since developers write these tests as they code.
3. Improves Code: It forces developers to improve the quality of their code.

Code Examples

Example 1: Statement Coverage

def add(a, b):
    return a + b

In this simple function, the statement coverage technique would involve writing tests that ensure the return statement is executed.

Example 2: Decision Coverage

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

For decision coverage, you would write tests that ensure both the if and else branches are executed.

Example 3: Path Coverage

def calculate(a, b, operation):
    if operation == 'add':
        return a + b
    elif operation == 'subtract':
        return a - b
    else:
        return "Invalid operation"

For path coverage, you would write tests that ensure all paths (add, subtract, and invalid operation) are executed.

Summary

In this tutorial, we covered the basics of White Box Testing, its techniques, and how it can help improve your code's quality and catch bugs early in the development phase. The next steps would be to learn about specific tools that can help automate this process, like JUnit for Java or pytest for Python.

Practice Exercises

Exercise 1: Write a function that divides two numbers and use statement coverage to write tests for it.

Exercise 2: Write a function that determines if a number is positive, negative, or zero and use decision coverage to write tests for it.

Exercise 3: Write a function that performs different calculations based on a given operation and use path coverage to write tests for it.

Keep practicing these techniques with different types of functions and applications to hone your White Box Testing skills.