White Box testing and Black Box Testing. What’s the Difference?

White Box Testing and Black Box Testing

Black box and White box testing are used to test the software application. Both of them follow different techniques and have different tools depending on the type. Both of these are used to detect bugs and defects in the software and the tester can fix them to deliver fully working bugs-free software.

White Box Testing

White Box Testing is the method in which the internal code is visible for the tester. The tester can go through the design and structure part of the code and verify the software's input-output flow. It is also known as Transparent box testing because the whole code is visible to the tester. 

The purpose of using the white box testing method is to test the inner working of the software. This testing method is also used to improve the software's design and security.

Points verified in software by white box testing

The white box verifies the software code for various purposes. Some of them are as follows.

• It verifies the working of conditional loops whether it functions correctly.
• The white box tests each part of the code individually whether it is a statement, function, or object.
• The white box also verifies the flow of inputs stream through the code.
• Similarly, it also checks whether the output is expected or not.
• It checks the structured path for some bugs and errors.
• The white box also verifies if there are any security holes in the internal structure.

Steps to perform White Box testing

To test an application with the white box the tester needs to follow two basic steps.

• Go through the entire code of the application.
  • Understanding the application's source code is very important while testing the code using the white box method. The tester must be aware of the language of the application. Checking the security of the application code is also important. While understanding the code tester must find out any security issues in the code and for that testers should be aware of secure coding practices.
• Test cases creation and executions.
  • In this step, the tester should test the proper flow and structure of the application. To test each process or a set of processes the tester should develop little test codes and execute them into the process. Therefore, the tester must have a deep knowledge of the coding languages to understand the code. 

White Box testing techniques

There are various code coverage techniques in white box testing. Some of them are as follows:

• Data Flow Testing.
• Multiple Condition Coverage.
• Branch Coverage.
• Decision Coverage.
• Finite State Machine Coverage.
• Path Coverage.
• Statement Coverage.

Each coverage technique has its own way to test the code. But to attain 90% of code coverage only two coverage can be used. Statement coverage and Branch coverage generally help cover most of the code.

In the Statement Coverage technique, each and every statement in the code is tested at least once during the testing process.

Whereas, in the Branch Coverage technique the path of the code which includes the if-else loops and other loops are tested in software testing.

Types of White Box Testing

Types of White Box Testing are as follows.

Unit Testing

Testing often starts with unit testing where each block of code is tested by the programmer. A programmer writes a block of code consisting of a function or an object and tests the code to avoid errors. Unit testing detects a majority of bugs.

Memory Leaks Testing

Memory leaking can affect the speed of the running application. A specialist who can detect memory leaks is needed to avoid memory leaks in an application.

White Box Penetration Testing

This technique is used to detect any security issues in the application. The tester has complete information about the application from source code to network information and server information. To detect any security issues the tester needs to execute the program from multiple points.

White Box Testing tools

The following are the top testing tools of White box

• HTMLUnit
• PyUnit
• EclEmma
• Parasoft Jtest
• CppUnit

Pros of White Box Testing

• Maximum converge is achieved with the help of coverage techniques and knowledge of the code by the tester.
• The White box optimizes the code.
• Similarly, we also use white box testing to remove extra lines in the code that can cause defects later in the functioning of the applications.
• By having the knowledge of the code, the tester can easily identify how to effectively test the application.

Cons of White Box Testing

• To work on the white box testing, skillful and complete knowledge of coding language is a necessity in a tester. Therefore the costs increases.
• If the code is lengthy the tester might skip some of the blocks of code for hidden errors which can affect the performance of the application.

Black Box Testing

Black Box Testing is completely different from White box testing. In this testing technique, the tester has to focus mainly on the input and output of the application. No need to understand the internal code of the application or any other information. 

The main focus is to check whether the applications fulfill the specifications and software requirements. Therefore, it is also known as Behavioural Testing because it only tests the working of the application by focusing on the input and output results.

Working of Black Box Testing

The following are the basic steps to follow to implement the black box testing technique.

• At first, the tester needs to understand the requirements and specifications of the software.
• The main focus is the input and output, so the tester executes some valid input in the software and checks whether SUT (System Under Test) processes them correctly. Similarly, the tester must also execute some invalid or false input in order to check whether the SUT detects the invalid inputs.
• After that tester should verify all the outputs expected for the respective inputs in the application
• If any error occurs, the tester should develop test cases for those inputs.
• Once the test cases are created. Tester executes them into the software and verifies the output.
• To test the result the tester should compare both the results.
• If the defects occur it needs to be fixed first and then a retest is required.

Types of Black Box Testing

There are various types of black-box techniques but the following are the main types of Black Box.

Functional testing

In Functional testing, the tester must fulfill the functional requirements in the software.

Non-Functional Testing

In this Testing type, the tester should consider the performance, the usability of the application while testing it. These are known as non-functional requirements because they are not mentioned in the software specifications and requirements but are important factors while testing an application.

Regression Testing

When a code is fixed or any updates are done on the current code then Regression testing is used to check whether the new code is working correctly as the existing code. Regression testing majorly occurs after system maintenance.

Tools of Black Box Testing

Depending on the different types of Black box testing use different tools. Some of them are as follows.

• QTP and Selenium are the automation testing tools which is used for Functional and Regression testing of an application.
• LoadRunner by MicroFocus and Jmeter by Apache are the tools used while performing non-functional tests.

Black Box Testing Techniques

Following are the different techniques in Black Box Testing.

Decision Table Testing

If there are any logical conditions or decision-making functions in the application, then use Decision Table Testing. The tester will execute the input and actions based on the conditions and generated the output. In this testing, we create a table with the input, output, and condition details. Each column consists of some unique values.

Boundary a Value Testing

This technique helps determine the range of the values accepted by a particular application. By determining this range, it will reduce the number of test cases. It is important to determine the boundary values those values can change the behavior of the system.

Equivalence Testing

This technique helps improve the test coverage and is time-saving. It divides the input values into different groups or classes. The output is considered while dividing the input into groups. Instead of executing different input values, a single value is executed for the group or class. Therefore it is a time-saving technique.

Difference Between Black Box and White Box Testing