What Is White Box Testing? (With Types And Advantages)

By Indeed Editorial Team

Published 25 April 2022

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

White box testing, otherwise known as open box, glass box, clear box or transparent box testing, is a technique that developers use to evaluate code and the internal structure of software. They typically perform this test during the coding phase of the software. If you are in or looking to join the software industry, it may be beneficial to understand this process to improve your skills and knowledge. In this article, we discuss what white box testing is, learn how to perform it, explore its types and techniques and look at its advantages, along with an example.

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What Is White Box Testing?

White box testing is a software testing method that developers use to evaluate a software's internal structure, design, coding and functionality. Developers often use this method to evaluate the input and output flow of an application, enhance its design and usability by identifying flaws and strengthen its security. It gets its name because it is a transparent method, and the code is visible to the tester during the process. A testing method in which the code is not visible to the tester is called black box testing.

Developers may use open box testing to analyse the following in the software:

  • Internal security weaknesses

  • Redundant code paths in the coding processes

  • The ability of the code to handle specific inputs

  • Expected output

  • The functionality of conditional loops

  • Individual testing of each function, statement and object

Related: How To Become A Software Tester: A Step-By-Step Guide

How To Perform Open Box Testing?

There are two main steps to perform open box testing:

1. Learn the source code

The first step to performing an open box test is to understand the source code properly. The tester generally requires a strong knowledge of programming languages to read the code and understand it. They may also require an understanding of secure coding practices to identify any security flaws in the code. Security is often one of the main reasons to test software. So, the goal is to find security concerns to prevent hacker attacks and malicious code from entering an application.

Related: A Guide On Black Box Testing (With Types And Strategies)

2. Perform the test

The next step is to evaluate the source code for correct flow and structure. The tester may use automation testing or manual testing to do this. In automation testing, the tester creates pieces of code, called scripts, that are run to perform a sequence of tests over the code. They may use various automation tools to achieve this. For manual testing, testers prepare test cases and follow specific test steps to perform the test. This process may take longer than automation testing.

Related: 40 Manual Testing Interview Questions (With Example Answers)

Open Box Testing Techniques

Here are some techniques that you can use to perform open box testing efficiently:

Statement coverage

A statement, in terms of programming, means a line of code. A statement becomes an executable statement when the tester is able to compile it. In open box testing, statement coverage means verifying that every statement is executable, and the tester tests it at least once.

Branch coverage

Branch coverage in open box testing refers to testing the possible outcomes of any piece of code. A branch is similar to IF statements. They can have two possible outcomes, true and false. Testers ensure that they execute both the outcomes of a branch and test for bugs.

Basis path testing

Basis path testing is a more comprehensive open box testing technique. It involves creating control graphs using flow charts or the application code. After this, the tester calculates the cyclomatic complexity of the graph, which helps in identifying the number of independent paths present in the code. The tester then designs test cases to test all the individual paths.

Cyclomatic complexity

Cyclomatic complexity is a software metric in open box testing that helps testers determine the complexity of a software program. It helps in identifying the number of decision points in a code. If the number of decision points is high, the complexity of the code is also high. A higher code complexity can increase the chances of errors and the time taken for the maintenance of the code.

Loop testing

Testers use loop testing to test loops in a code and identify bugs while executing the loops. It is a type of control structure testing. Loops testing can be further split into four types:

  • Simple loop testing: This involves testing a single loop in the code like for, while or do-while conditions. It helps testers evaluate whether the loop terminates after it meets the condition.

  • Nested loop testing: This helps in testing nested loops, which is a loop inside another loop. There may only be a finite number of nested loops and include for, while or do-while loops.

  • Concatenated loop testing: This type of testing involves testing loops present after loops. The difference between nested and concatenated loops is that a nested loop is inside another loop, while a concatenated loop indicates a series of continuous loops.

  • Unstructured loop testing: This involves testing loops that are unstructured. This may include a combination of concatenated and nested loops in no particular order.

Related: What Is The Role Of A Software Development Engineer In Test?

Types Of Open Box Testing

Here are some of the most common types of open box testing:

Unit testing

Programmers use unit testing to test pieces of codes as they develop them. Instead of testing the functionality as a whole, they perform the test on smaller units of the functionality during the development. This helps them identify any bugs or issues in the code during the early development stages. Resolving the bugs earlier can help programmers integrate the pieces of code easily, without errors. It is also convenient and economical to fix the bugs during development than to fix them after integration of the code blocks.

Integration testing

Integration testing is one of the main types of open box testing. It involves integrating several pieces of code to test them. The aim of this test is to see if the pieces of code work together as per the requirements. After integrating the pieces, testers run the code and identify any bugs or compatibility issues in the entire block. This allows them to fix the issues before they can integrate more pieces with that particular block. Integration testing can reduce maintenance costs by eliminating major issues before bundling the application.

Regression testing

Testers usually perform regression tests on the functionalities that they have already tested. This allows the testers to determine that the functionality does not misbehave after making changes to the code. They rerun the previous test cases to see if the feature run in the desired manner. This helps the testers to ensure that the old code still runs after making changes like adding functionalities or fixing bugs.

Penetration testing

Penetration testing requires the tester to have in-depth information on the source code, network, server and IP addresses. The aim of this test is to launch authorised cyberattacks at the application to check for potential vulnerabilities. This test is also known as ethical hacking and can be extremely useful in identifying security issues within an application.

Mutation testing

Mutation testing can be useful in creating robust code. It involves making small changes to different parts of the code to see if the application can detect those. The aim is to invoke errors when the application detects the changes. Each change in the code is known as a mutant. Mutation testing can help in identifying weak code blocks and strengthen them.

Related: 30 Interview Questions For Software Developers (With Answers)

Advantages Of Open Box Testing

Depending on the software application size, testing can often be a complex job. To minimise its complexity at each software development stage or during modification, testers conduct open box testing. Here are some advantages of open box testing:

  • Allows code optimisation for finding bugs

  • Enables complete code testing, providing a thorough examination

  • Allows easy automation

  • Allows testing from the initiation of the development stage

Related: List Of 11 Important Automation Testing Tips (Plus Benefits)

Open Box Testing Example:

The goal of open box testing is to confirm all the loops and decision branches in the code. Here is a simple example of this:

void Printme (int c, int d) // Printme is a function
int I = c + d ;
If (I > 0)
Print ("Positive",I) ;
Print ("Negative",I);
} // End of the source code

To practice using the statements in the above code, you can use the following open box test cases:

  • C = 1, D = 5

  • C = -5, D = 3

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