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White box testing is a method to evaluate how software operates by examining the code’s logic. It assists in identifying issues early by assessing aspects such as logic, loops, and conditions. To conduct this evaluation, you must possess a strong understanding of the code. This method enhances the software’s dependability and facilitates fixes before it is delivered to users. It is beneficial for developers to confirm that every segment of the program performs as intended.

In this article, you will discover a comprehensive explanation of white box testing with the aid of an example.

Table of Contents:

• What is White Box Testing?
• Types of White Box Testing
• White Box Testing Techniques
• What Does White Box Testing Focus On?
• Process of White Box Testing
• Features of White Box Testing
• Tools Used for White Box Testing
• Advantages of White Box Testing
• Disadvantages of White Box Testing
• Best Practices for Black Box Testing
• Real-World Applications of White Box Testing
• Black Box vs White Box vs Gray Box Testing
• Conclusion

What is White Box Testing?

White Box Testing is a form of software evaluation where the internal architecture, design, and code of the software are examined. It inspects the code to determine how it functions.

It is also referred to as clear box testing, glass box testing, transparent box testing, and structural testing.

For instance, if you are assessing a vehicle using white box testing, you would examine the internal mechanisms, such as the engine, wiring, and other internal components, to ensure that everything operates correctly.

Types of White Box Testing

There are primarily 3 categories of white box testing. These include:

1. Unit Testing

In this form of testing, individual units of the code are tested in isolation, such as a single method or function. Developers primarily conduct this to verify that each section of the code operates correctly. This method facilitates quick and automated identification of code errors.

For instance, if you have a method called add(), you would examine various values to ensure it produces accurate or inaccurate outcomes. If it yields an incorrect result, you would investigate the cause of this unexpected output.

2. Integration Testing

This testing type evaluates multiple units or modules collectively to assess how they function as a cohesive unit. It is performed by developers or testers following unit testing completion. This approach unveils bugs when different components or modules interact.

For example, you would test the login and registration processes of an application. In this case, both the coding and the database for these modules would be assessed.

3. Regression Testing

In this kind of testing, the software is evaluated post-code modifications, such as bug fixes or feature additions. Testers or automated systems typically perform it, and sometimes developers involved in an agile team also conduct this testing.

The primary goal of regression testing is to ensure that the core functionality of the code remains unaffected after changes are applied.

For example, if you introduce a new payment method in an application, you would need to re-execute the tests or the entire application to confirm that no errors arise following the update.

Note: Regression testing can be classified as either white box or black box, based on the testing level at which the tests are constructed.

White Box Testing Techniques

White Box Testing employs the following techniques to examine each aspect of the application, ensuring that every minor error in the code is scrutinized. These methods include:

1. Statement Coverage

Statement Coverage guarantees that every line in the program is executed at least once, regardless of its simplicity. It represents the foundational form of white box testing, ensuring that no line of code remains untested.

As shown in the flowchart above, there are 2 possible statement coverages, namely via ACG and via ABDG.

2. Branch Coverage

Branch Coverage ensures that all conditional statements, such as if-else, are evaluated for both true and false results. Its primary goal is to confirm that each possible decision is tested at least once while also validating the decision logic of the statement.

In more complex scenarios, this may increase the number of necessary test cases.

In the preceding flowchart, it is evident that there are primarily four branches of coverage: ACG, ABG, ABDEG, and ABDEFG.

3. Condition Coverage

This method involves evaluating every Boolean sub-condition within the code. It guarantees that each condition inside a decision block is assessed for both true and false outcomes.

For instance,

if (A && B) {
    // execute something
}

In the given condition,

A = true, B = true

A = false, B = true

A = true, B = false

A = false, B = false

The if block will only execute when both conditions are true; therefore, all variations of A and B must be tested independently.

4. Path Coverage

This technique verifies every possible path in the code, including various combinations of branches, to identify complex bugs by exploring every potential flow.

public void process(int x) {
    if (x > 0) {
        if (x % 2 == 0) {
            System.out.println("Positive Even");
        } else {
            System.out.println("Positive Odd");
        }
    } else {
        System.out.println("Non-Positive");
    }
}

In the above example, the potential paths of the code may include,

• x > 0, x % 2 == 0, Positive Even
• x > 0, x % 2 != 0, Positive Odd
• x <= 0, Non-Positive

Therefore, a minimum of three test cases is necessary to navigate all paths.

5. Loop Testing

Loops are foundational aspects of coding challenges and are utilized in nearly every functionality of software. The testing of loops can be categorized into simple, nested, and concatenated structures, as outlined below:

For Simple Loops

For a loop that executes n times, you should test it with:

• Test with a value that causes the loop condition to be false from the outset.
• Test with a value that permits the loop to run precisely once.
• Test the loop one less than its typical maximum.
• Test with a value lower than the full loop count.
• Test with a value higher than anticipated.

for(int i=0;i<n;i++)
{
      //code
}

For example, if n equals 5, then according to the above scenarios, the loop will

• Not execute if n equals 0
• Run once if n equals 1
• Execute 4 times if n equals 4
• Run m times, where m<n (with m as 3)
• Encounter logic errors if m equals 6 (where m>n).

This approach helps identify bugs when loops execute too few or too many times.

For Nested Loops

for(int i=0;i<n;i++)
{
     for(int j=0;j<m;j++)
     {
           //code 
     }
}

These loops occur within other loops. To test them:

• Begin with the innermost loop.
• Test it as if it were a simple loop.
• Then examine the outer loops step-by-step.

This technique captures problems in deeply nested code.

For Concatenated Loops

These loops are sequentially arranged one after another.

• If the loops are independent, test each like a simple loop.
• If they are dependent, test them as nested loops.

This ensures that every loop functions correctly, whether in isolation or connected to others.

What Does White Box Testing Center On?

1. Control Flow: This assesses conditional statements, loops, and nested structures, among others.

2. Code Coverage: One of the pivotal focuses of White Box Testing is to enhance code coverage. It guarantees that no section of the code remains unexamined.

3. Logic and Decision Testing: White Box Testing verifies the logical determinations within the code. Its primary objective is to uncover logical errors that may be overlooked in Black Box Testing.

4. Internal Functionality and Algorithms: It ensures the accuracy of an algorithm, its boundary conditions, performance, and edge cases. Its primary function is to evaluate the internal processing of the application.

5. Data Flow: It also examines how data is managed within the code, covering aspects like variable initialization, variable scope, among others.

6. Error Handling and Exception Flow: It assesses how the code manages errors and unforeseen circumstances. Its primary aim is to ensure the software’s robustness and dependability.

White Box Testing Procedure

Now, let’s delve into how the white box procedure is initiated and how testing is accomplished.

1. Input

This is the initial phase of the White Box Testing procedure. It begins with collecting all specifications and accompanying documents.

• Requirements: This outlines the functions the software must perform for given inputs and the anticipated output.
• Functional Specifications: This indicates how the software should operate under various conditions as dictated by user needs.
• Source Code: This represents the code crafted by the developer based on the requirements provided by the user. Here, the primary functionality and logic of the code are established.

2. Processing

After the input is provided, the next step is processing.

• Risk Analysis: In this phase, the principal risk within the code is identified, considering the software’s functionality. Testers focus on areas where errors are likely to occur.
• Test Planning: In this stage, the testers devise test cases that encompass all software conditions, such as loops, functions, and requirements.

3. Test Execution

Once the test cases are formulated for the applications detailed above, this phase involves verifying them.

• Execute the tests: The devised test cases are evaluated. Furthermore, during the execution of these test cases, the core logic of the application is also scrutinized.
• Error identification and resolution: Should any errors emerge during the previous phase, they are reported to the development team for rectification. Post fixing, the development team reruns the test cases for software verification.

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• Step is retained until the primary issues are addressed within the application.

4. Results

Upon completing the testing by rectifying all software errors, the concluding phase is executed.

Final Report: During this phase, a comprehensive report of the software is generated, encompassing all test cases, errors, and the modified code. This documentation provides an extensive overview of the test cases and the software’s functionality. The procedure of white box testing. This cycle is reiterated should the previous steps uncover defects within the software.

Characteristics of White Box Testing

The following outlines the prevalent characteristics of White Box Testing.

1. Demands Familiarity with Source Code: The code is scrutinized from the inside, meaning a prior understanding of the code is necessary for effective testing. For instance, evaluating an if condition.

2. Evaluates Logic Flow and Decision-Making: It analyzes the logical flow to ascertain how the program reaches decisions. For example, if age>18, the individual is permitted to vote.

3. Encompasses All Branches and Pathways in Code: It examines every branch of the code, including if-else statements, loops, and more.

4. Can Initiate Before UI Development: This form of testing can commence prior to the creation of the UI or frontend of the website.

5. Utilized in Unit Testing: It plays a crucial role in unit testing, assessing individual functions of the software.

6. Assists Uncover Concealed Bugs: It aids in identifying bugs that real-world users might miss.

7. Facilitates Automation with Tools Like JUnit: Automation tools such as JUnit can be employed to create test scripts suitable for automation.

Instruments Employed for White Box Testing

A variety of tools are available for white box testing; some of the notable tools are examined below:

1. JUnit: This is utilized for writing and executing unit tests in Java.

2. NUnit: This resembles JUnit but is designed for C#.

3. PyTest: A widely-used Python testing framework.

4. CppUnit: A tool aimed at testing the C++ language.

5. JaCoCo: Java Code Coverage is a utility that verifies which sections of the code have been tested, specifically for Java.

6. SonarQube: It assesses code quality and test coverage, detecting untested code and bugs in Java, C#, and other programming languages.

Next, we will explore the merits and drawbacks of white box testing.

Advantages of White Box Testing

1.  It inspects the code internally to ensure that every line, condition, and loop undergoes testing.

2. Since this testing is conducted in the initial stages of development, issues can be identified and corrected before the software launch, ultimately saving time and reducing costs later in the project.

3.  It aids in recognizing unnecessary code segments or parts destined never to execute, which can be eliminated, enhancing code efficiency.

4. Automated tools like JUnit, PyTest, or NUnit can be employed to create white box tests once and then run them automatically when modifications are made to the code.

Disadvantages of White Box Testing

1. The individual conducting the testing must possess solid coding skills; a person lacking this knowledge will struggle to perform effective testing.

2. Exploring all potential code paths in large or complex applications can be labor-intensive and mandate considerable effort to maintain.

3. Its concentration is solely on the code of the program; therefore, it does not evaluate how the application appears to users.

4. When the internal code structure changes, numerous existing tests may cease functioning and require updates.

Best Practices for White Box Testing

Numerous common errors are made by users. Below are some advisable practices to help users avoid frequent mistakes while conducting white box testing.

1. Before commencing testing, carefully compile a list of requirements or specifications.

2. Construct test cases that account for all types of inputs, including valid inputs the software should accept, invalid inputs to assess error handling, and boundary input values at extreme levels, such as minimum and maximum.

3. Prior to deploying test cases, review your test cases independently, which may help identify issues that some test cases might overlook.

4. Many bugs occur at the thresholds of input ranges; thus, pay thorough attention to the edges.

5. Utilize automation tools to expedite the process and minimize errors.

Real-World Utilizations of White Box Testing

1. White box testing is employed where unit testing is necessary for individual functions or methods.

2. It is utilized for identifying security vulnerabilities within code, such as SQL injection, buffer overflows, or improper access control.

3. White box testing is essential for applications laden with business rules or calculations to ensure that all conditions are tested.

4. White box testing holds significant importance in critical sectors like healthcare, aviation, or finance, where minor bugs could lead to severe consequences.

5. In contemporary development (DevOps), white box tests are executed automatically whenever the code is modified to catch errors early.

Black Box vs White Box vs Gray Box Testing

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Feature	Black Box Testing	White Box Testing	Gray Box Testing
Code Knowledge	No access to code	Complete access to code	Partial access to code knowledge
Tester Role	Quality Assurance specialists	Developers	Technical testers
Testing Focus	External functionalities	Internal code architecture	Integrated approach
Basis for Tests	Requirement documentation	Source code	Limited design documentation
Example Tests	Form validation	Branch coverage	API integration
Best For	User experience	Code quality	System integration
Advantages	User perspective	Comprehensive evaluation	Equitable methodology
Constraints	Overlooks coding errors	Resource-consuming	Limited perspective

Summary

White box testing refers to inspecting the code internally to ensure all components function correctly. It aids in identifying errors early and enhances the quality and speed of software. Some coding knowledge is required to execute it, but it facilitates the testing of every segment of the application. With effective tools, locating and resolving issues becomes more manageable. It’s a prudent strategy to develop robust and faultless software.

If you wish to delve deeper into this subject, you can check our Java course.

What is White Box Testing? – FAQs

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