Black Box Vs. White Box Testing: The Key Differences

Black box testing and white box testing are not the same. They evaluate the functionality, performance, and security of a software application.

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1. Black box testing
   1. Example: Testing Login Functionality
2. White box testing
   1. Example: Testing a Function to Calculate the Sum of an Array

Black box testing

• Black box testing is a method of software testing that checks how an application works without looking at its internal structures.
• This method of testing can be used for different levels of software testing: unit, integration, system, and acceptance. It usually includes higher-level testing, but can also include unit testing.

Example: Testing Login Functionality

In the context of a web application, we can focus on the black box testing of the login functionality. This example aims to explain the concept of black box testing rather than detailing the entire testing process.

Functionality

The login functionality allows users to enter their credentials (username and password) to access their account.

Test Cases

1. Test case 1: Valid credentials – Enter the correct username and password, and expect a successful login.
2. Test case 2: Invalid credentials – Enter incorrect username and password, expect login failure.
3. Test case 3: Empty username – Enter empty username and valid password, expect login failure.
4. Test case 4: Empty password – Enter a valid username and empty password, expect login failure.
5. Test case 5: Password with special characters – Enter a valid username and password with special characters, and expect a successful login.
6. Test case 6: Username with more than maximum length – Enter username with more than the allowed maximum length, expect login failure.

Testing Approach

For black box testing, we focus on testing the functionality without internal knowledge of the code. The following steps are typically involved:

1. Identify test cases based on the requirements and specifications.
2. Design input data based on valid and invalid scenarios.
3. Execute the test cases, providing the inputs and verifying the expected output against the actual outcome.
4. Document the test results, including any defects or issues found.

This example demonstrates how black box testing focuses on the input and expected output, without examining the internal implementation details of the login functionality. The goal is to ensure that the functionality behaves correctly under various scenarios, regardless of how it is implemented.

White box testing

• White Box testing is a type of testing that focuses on examining the internal structure and code of an application. It is also known as clear box testing or transparent box testing.
• It tests the internal structures or workings of an application, as opposed to its functionality (black-box testing).
• Testers use an internal perspective of the system and programming skills to design test cases. They select inputs to test different paths in the code and find the correct results.
• White-box testing can be performed at the unit, integration, and system levels of the software testing process. It is now used more often for integration and system testing.
• It can test different paths within a unit, paths between units during integration, and between subsystems during system-level testing.
• While this method can find many errors or problems, it might miss parts of the specification that have not been implemented or requirements that are not included.

Example: Testing a Function to Calculate the Sum of an Array

In the context of a Python program, let’s consider white box testing of a function that calculates the sum of elements in an array. The purpose of this example is to illustrate the concept of white box testing, not to implement the entire testing process.

Functionality: The function calculate_sum(arr) takes an array arr as input and returns the sum of all elements in the array.

Test Cases:

1. Test case 1: Empty array – Pass an empty array as input, expect the sum to be 0.
2. Test case 2: Positive integers – Pass an array of positive integers as input, expect the sum to be the sum of all elements.
3. Test case 3: Negative integers – Pass an array of negative integers as input, expect the sum to be the sum of all elements.
4. Test case 4: Mixed integers – Pass an array of mixed positive and negative integers as input, expect the sum to be the sum of all elements.
5. Test case 5: Floats – Pass an array of floating-point numbers as input, expect the sum to be the sum of all elements.
6. Test case 6: Large array – Pass a large array of integers as input, expect the sum to be the sum of all elements.

Testing Approach

For white box testing, we focus on testing the internal implementation of the function. The following steps are typically involved:

1. Understand how the function works, including any steps or rules it follows.
2. Create test cases to cover all parts of the code, including special cases, positive/negative scenarios, and unusual situations.
3. Provide input values to the function based on the test cases and run the function.
4. Compare the expected output with the actual output.
5. Analyze the program’s logic to find any potential errors or problems.
6. Update the test cases or add new ones based on the code’s coverage and analysis.

This example demonstrates how white box testing involves examining the internal structure and implementation details of the function to identify potential issues, like incorrect calculations or control flow problems. The goal is to verify that the function performs as intended and to ensure all paths within the code are thoroughly tested.