White Box Testing : Complete Guide

April 12, 2020

What is White Box Testing?

The term ‘White Box’ is used to refer to a transparent or glass box, through which the internal structure of a product is visible, and which allows the team to analyze, evaluate as well as explore the workings of an application’s internal structure. White Box Testing, which is also known as glass box testing, tests the internal structure of an application product through the derivation of test data from the program logic.

This type of software testing technique is also known by other names, such as open box testing, structural testing, logic driven testing and clear box testing.

white-box testing

Black box testing, which is a counterpart of white box testing, does not involve the testing of the internal structure and framework of the application, rather, it evaluates the quality of the system externally from the perspective of the end user.

Features of White-Box Testing:

An integral part of software testing life cycle (STLC), white box testing is a method of testing a software or application, wherein the test manager evaluates the internal structure, code, as well as the workings of the software. It ensures that no hidden errors impact the effectiveness and the functioning of the product, by thoroughly testing its code and other internal aspects. In short, white box testing guarantees an error free environment by validating and testing fragile or defect prone codes.

Few of the other important features of white box testing are:

It is used by both, software testers and developers to validate the quality of a software product’s internal structure.
Helps the team determine the line of codes that are executed.
It can be applied to various testing levels, like unit testing, integration testing, and regression testing.
Validates the quality as well as the accuracy of the testing data.

White Box Testing Levels

As stated above, white box testing can be executed during various software testing phases to validate the effectiveness of the internal structure as well as to ensure the accuracy of the written code. The three major testing stages, where white box testing is applicable are:

Unit Testing: During unit testing, white box testing tests the code to validate that it is working as intended and is free of any defects or issues. Moreover, it detects the defects before the code is integrated with already tested code, which further prevents any defects from occurring in later stages of testing. White box testing in unit testing is performed in isolation.
Integration Testing: In Integration testing, the interaction between interfaces is tested with the assistance of white box testing. Performed in an open environment, here white box testing ensures the correctness as well as the accuracy of the interfaces.
Regression Testing: At this stage of software testing, the white box test cases created during the earlier two stages are recycled and tested again.

White-Box Testing Infographic

What All is Tested Under White Box Testing?

White box testing is employed to check the following aspects of a software product:

Checking for loopholes in internal security features.
Detecting poorly structured paths in coded structures.
Proper functioning of conditional loops.
The smooth flow of input data through the code.
Individual testing of every object or functionality related to the product under test.

WhiteBox Testing Techniques:

White box testing can be executed with the assistance of three major techniques, which are mentioned below.

Statement Coverage: A code of instructions remains a statement until it gets compiled for errors and becomes part of the code structure. In statement coverage technique of White box testing, each and every statement which is part of the code structure, gets verified at least once.
Branch coverage: This technique checks every single entity having a conditional loop around a decision point, such as If-Then-Else statements.
Path coverage: A technique more powerful than both statement & branch coverage, path coverage, as the name suggests, verifies every single path of an application at least once.

white box testing techniques

Read more about these white box testing approaches in our related article.

Importance of Code Coverage in White Box Testing:

Apart from statement, branch, and path coverage, white box testing uses code coverage, which is another major testing technique that is used to validate the correctness of the code. As white box testing is a code based testing, code coverage allows it to effectively eliminate gaps in the test case suites. Moreover, this technique enables the team to identify areas of the program that are not exercised by a particular set of test cases and ensures that the test cases are actually testing all lines of code. Furthermore, the criteria for code coverage is also considered by the team in white box test design technique, which are:

Furthermore, the criteria for code coverage is also considered by the team in white box test design technique, which are:

Control flow Testing.
Data flow Testing.
Decision Coverage.
Modified Condition.
Prime path testing.

White Box Testing Process

White-box testing follows a designated testing process, wherein each aspect of the software is tested thoroughly by the team or the test manager, to ensure its accuracy as well as quality. The process of white box testing includes five important steps, which are:

working of white box testing

Understanding and Evaluating Code: Making use of the biggest advantage of white box testing, the tester should have an in depth knowledge of the source code.
Resource Management:He should make himself well versed with the programming language used as well as the intricate tools and subtle nuances involved in the development of the software product being tested.
Test Case Creation:Creation of tests cases for each step, path or branch of instruction either individually or in combinatorial form.
Test Execution: Execute test cases via hit and trial methods, manual testing or automation.
Test Result Generation: A final summary is generated noting down all the preparation details and the results achieved.

WhiteBox Testing Advantages:

White-box testing has edge over black box testing in revelation of hidden errors in the code.
White box testing is fairly easy to automate, allowing reduction in testing time.
Helps spot dead codes in accordance with prevalent testing practices.
White box testing enables easy traceability of the tests right up to the source level. This way any future changes in software to be congruently captured for changes in the tests.
The white-box testing can be commenced at an earlier stage of software development life cycle (SDLC).
This type of testing is more thorough and covers most paths and codes of the software.

White Box Testing Disadvantages:

Not possible to cover every possible condition for testing.
Since this testing approach requires a thorough understanding of the software, the testing effort requires the services of a tester having ace programming skills.
It is time consuming, complex, as well as expensive.

Difference between White Box Testing, Black Box Testing, and Gray Box Testing:

To understand the significance of white box testing in software testing life cycle (STLC), it is important to compare it with its counterparts- black box testing and gray box testing. By doing so, one can garner more information about white box testing and enhance their basic knowledge about it. Therefore, following is a comparison of WhiteBox, Black Box, and Gray Box Testing.

White Box Testing	Black Box Testing	Grey Box Testing
1. Testers have full knowledge of the internal structure of the software.	1. Black box testing is not concerned about the internal workings of the software, hence, it has no knowledge of it.	1. Limited knowledge about the internal structure as well as working of the software is available.
2. Known as glass box, open box, or code based testing.	2. Known as closed box or data driven testing.	2. It is also known as translucent testing.
3. It verifies the security gaps in the code and internal structure of the software.	3. It is mainly concerned with the external functionality and behavior of the software.	3. Here, both, white and black box testing are used by the team of testers.
4. Performed by a team of software testers and developers.	4. This type of testing is either performed by the testers/developers or the end users.	4. Like black box testing, gray box testing is also performed by end users and testers.
5. It is one of the most exhaustive and time-consuming testing technique.	5. It is time and cost effective testing technique.	5. It is partially time consuming and comprehensive.

Get a better insight into the differences between these testing techniques from our article White Box Testing VS Gray Box Testing VS Black Box Testing.

White Box Testing Tools:

A software testing process can be improved and simplified with the aid of various automated tools available in the market. Similarly, to enhance the accuracy as well as the quality of testing, software testers around the world perform white box testing with the assistance of various tools like:

white box testing tools

In nutshell, it may be inferred that the use of white box testing approach, for the early identification of faults in code or in detecting dead code(s), not only ensures the higher quality & lesser complexity of the code but also minimizes the probability of occurrence of any unexpected issue or defect at a later stage in future. Hence, by implementing it during early stages of software development life cycle, the team of testers can ensure optimum quality as well as the efficiency of the product.