What is White Box Testing? Types, Examples & Techniques

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White-box testing assesses a software’s internal structure: codes, architecture, and interfaces. It calls for a knowledge of programming languages and secure coding practices.

What is White Box Testing?

White-box testing is a Quality Assurance process to examine the inner working of an application. The code will be visible to the tester.
Also known as glass-box, clear-box or transparent-box, or open-box testing, it lends a granular view by targeting the source code. This dynamic testing process evaluates the design for stability and applies to all levels of SDLC.

The white-box tests are based on the coverage of code statements, branches, paths,s and conditions. By validating the input-output flow, they leave the application reliable and secure. These tests can be carried out at unit, integration, and system levels to check if the software yields the desired results.

An open-box test flags internal security vulnerabilities and redundant code paths and traces the input-output flow paths in the system. It verifies if an application responds accurately to input while staying immune to hacking attempts.



White-Box Testing Techniques

Several white-box testing techniques are available to scrutinize software. Among these, the  Code-Coverage Analysis is widely used to enhance the effectiveness of code testing. Various white-box testing techniques are as follows:-

  • Statement coverage: This technique exercises each line of code at least once.
  • Branch coverage: This technique examines the accuracy of each possible path or decision point of a software application.
  • Condition coverage: All individual conditions are checked.
  • Multiple condition coverage: All combinations of all conceivable condition outcomes are tested at least once.
  • Basis path testing: A control flow graph is prepared to calculate the cyclomatic complexity so that the minimum number of test cases can be designed for each path.
  • Flow chart notation: This technique uses a directed graph made up of nodes and edges, where each node represents a decision point or sequence of statements.
  • Cyclomatic complexity: This is the measure of a software's logical and cyclomatic complexity and defines the number of independent paths present.
  • Loop testing:   This technique checks the reliability of loops, and involves simple, nested and concatenated loops.

Types of White-box testing

Different tests are held to ascertain the usability of an application or a specific software package:

Unit testing

In this method, each block of code is tested as it is developed. It helps identify errors at the beginning of the development process, thus reducing the cost of code-fixing.



Quality assurance test

QA test targets codes to identify performance issues linked to memory leaks. Poorly designed codes fail to clear memory segments, thus slowing down the application. 

Penetration testing

The technique simulates cyber-attacks to find out the application's security weak spots.

Mutation testing

The process induces faulty codes to see if the test cases are capable of detecting them. It looks at the adequacy of test cases.

White-Box Testing Example 

Consider the following piece of code

sum(int a, int b) {
  int result = a+ b; 
  If ( result > 0)
        print ("Positive", result)
        print ("Negative", result)

To exercise the statements in the above white box testing example, WhiteBox test cases would be
a = 1, b = 1
a = -1  b = -2

White-box Testing Tools

A few White-box testing tools are discussed below:-

a) JSUnit.net

This JavaScript testing tool is a part of Junit and constitutes an open-source unit testing framework. 

b) CppUnit

CppUnit is also considered to be a part of JUnit. The tool can provide the output in plain text or XML format, and creates unit tests with its own classes.

c) NUnit

It’s a unit testing framework written in C#. The tool supports all available .Net languages and is suitable for data-driven tests. It allows both parallel and concurrent execution and provides a class framework and test runner apps. It’s relatively easier to use.

d) JUnit

JUnit is a unit testing automation tool for Java. and can be easily integrated with IDEs such as Eclipse, Maven  ACT, etc. It supports test-driven development and helps synchronize existing tests with newly created ones. 

e) CSUnit

 CSUnit permits unit testing in the .Net Framework and supports languages such as C# and VB.Net. CSUnit has built-in support for factoring.

 Advantages of White-Box Testing

  • Aids in Code optimization 
  • White box test- cases can be easily automated.
  • Ensures a high code-path coverage
  • Allows testing from the early stages of  SDLC even if GUI is not available.

Codes govern the conduct of an application, and a White-box test inspects the codes. Hence it’s a vital step towards software that is secure, reliable, and trustworthy.

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