What is black box and white box testing?
Published: 2023-09-25 14:25:44


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/zedbq6zo7vw99wftw6gk.jpg)Black box testing and white box testing are two distinct approaches to software testing, each with its own characteristics and purposes. Let's dive deeper into each of them with examples:

1. Black Box Testing:
Black box testing is a method where the tester focuses on examining the functionality of a software application without having any knowledge of its internal structure or code. Testers treat the software as a "black box" and validate its outputs based on the given inputs. They typically rely on requirements or specifications to design their test cases. Examples of black box testing techniques include:

a. Equivalence Partitioning: In this technique, the input domain is divided into equivalence classes, and test cases are designed to cover each class. For instance, if a system accepts a range of values (e.g., 1-100), test cases may include values from each partition, such as 5, 50, and 95.

b. Boundary Value Analysis: This technique focuses on testing the boundaries or edge conditions of inputs. For instance, if a system accepts values from 1 to 100, test cases may include values such as 1, 2, 99, and 100 to ensure the system behaves correctly near the boundaries.

2. White Box Testing:
White box testing, also known as clear box testing or structural testing, involves examining the internal structure and code of a software application. Testers have access to the source code and use their knowledge to design test cases that exercise specific paths or conditions within the code. Examples of white box testing techniques include:

a. Statement Coverage: This technique aims to ensure that every statement in the source code is executed at least once. Test cases are designed to cover different code statements, increasing the likelihood of uncovering errors or bugs.

b. Branch Coverage: In this technique, the goal is to test every possible branch or decision point within the code. Test cases are designed to exercise both the true and false branches to ensure all logical paths are tested.

It's worth noting that black box testing and white box testing are not mutually exclusive. They both play crucial roles in a comprehensive testing strategy. Black box testing focuses on the external behavior of the software, while white box testing delves into the internal workings. Using a combination of both approaches ensures a thorough testing process and helps identify a wider range of defects or issues within the software.

 Examples of black box testing and white box testing for a hypothetical login functionality of a software application:

1. Black Box Testing Example:
Assuming the login functionality requires a username and password, a black box tester might design test cases as follows:

Test Case 1:
Input: Username: "john.doe@example.com", Password: "password123"
Expected Output: Successful login

Test Case 2:
Input: Username: "jane.smith@example.com", Password: "wrongpassword"
Expected Output: Login failed with an appropriate error message

Test Case 3:
Input: Username: "", Password: "password123"
Expected Output: Login failed with an appropriate error message

The black box tester focuses on the expected behavior and validates the output based on different input combinations without considering the internal implementation.

2. White Box Testing Example:
Assuming the login functionality includes additional checks, such as password encryption and username validation, a white box tester might design test cases as follows:

Test Case 1:
Input: Username: "john.doe@example.com", Password: "password123"
Expected Output: Successful login

Test Case 2:
Input: Username: "jane.smith@example.com", Password: "wrongpassword"
Expected Output: Login failed due to incorrect password validation

Test Case 3:
Input: Username: "john.doe@example.com", Password: "password123"
Expected Output: Login failed due to incorrect username validation

The white box tester examines the code and designs test cases to cover specific paths or conditions within the code, ensuring that all branches and statements are tested.

Black Box vs. White Box Testing: Understanding simple 3 keys.

Black box testing is defined as a software testing methodology in which the tester analyzes application functionality without a thorough knowledge of its internal design. Conversely, white box testing is defined as a software testing methodology in which the tester’s knowledge of the application’s internal workings is leverage during testing.

Black box testing is a software testing methodology in which the tester analyzes the functionality of an application without a thorough knowledge of its internal design. Conversedesign of the application and analyzes it during testing
The term black box symbolizes a black outer covering of the application, preventing testers from seeing its inner workings and compelling them to examine only the end-user experience. Likewise, the term white box signifies the application’s transparency, allowing the tester to see through the outer box and into the inner code.before
In black box testing, the testing team analyzes the workings of an application without first having an extensive understanding of its internal structure and design. During testing, the input value is simply compared with the output value. Due to its nature, black box testing is sometimes called specification-based testing, closed box testing, or opaque box testing.

Black box testing mainly focuses on the comprehensive examination of application functionality. It is closely related to behavioral testing and behavioral testers may have limited knowledge of internal application workings.

The black box methodology is used to test most 
modern software applications
. It covers numerous test cases, allowing maximum bugs to be discovered. This testing method is used at all stages of the software development cycle.

Black box testing focuses on understanding user experience, which means testers do not require in-depth technical knowledge to carry it out.

What Is White Box Testing?
The software application’s internal coding, design, and structure are examined in white box testing to verify data flow from input to output. White box testing is leveraged to improve design, usability, and 
application security
. The other names for this methodology include code-based testing, glass box testing, open box testing, clear box testing, and transparent box testing.

 white box testing is intensive. Combined with other bug-quashing techniques, it is a robust quality assurance tool.

The granularity offered by white box testing is an effective way to crush bugs. This transparent and rigorous testing approach also gives insights into all the possible outputs the application can theoretically generate. White box testing is leveraged to spot hidden internal errors and optimize code.

QA teams usually subject every facet of an application through black box testing procedures. However, white box testing is generally arranged solely for the most critical components of an application. This is due to the resource-intensive nature of white box procedures. It is deployed for applications such as payment remittance and national security–features that have the potential to affect living conditions directly and, thus, cannot afford to fail.


Differences Between White Box Testing and Black Box Testing


Both black box testing and white box testing have advantages and disadvantages.Here the three primary distinction between the two software testing.

1. Process

The black box testing procedure promotes a rigorous and comprehensive approach to application analysis. The goal is quality assurance for the end user.
The process begins with the testing team understanding the requirement statement of the application. This step generally requires the presence of a well-documented software requirement specification.

Testing methodologies such as equivalence partitioning and boundary value analysis are used to determine sets of valid inputs and their predicted outputs.

This information is then used to build test cases, which are then run to check whether they are successful or not.

The actual outcomes are compared against the intended outcomes, and failed test cases are classified as bugs or defects.

These bugs are reported to the development team, who then work on fixing them.

Once the developers update the application, the testing team retests the previously reported problem areas and checks if they have been fixed.

The white box testing process is much more ‘surgical’ than black box testing and far more effective on smaller targets. The goal is to assess all the possible cases and scenarios for the target, which is often a ‘too-critical-to-fail’ application, component, or functionality.
The first step is identifying the target: the component, feature, or application to be tested. By choosing a narrow target, white box testers can be thorough and ensure flawless functionality. This is usually achieved by picking the smallest possible logical module, working on it and then moving on to the next one.

Of course, one can also execute white box testing on larger systems; however, this is often a resource-intensive process and should only be done if the need is greater than the effort.

The next step is creating a flow graph by plotting all possible scenarios. This helps determine the scope of the testing exercise and write relevant test cases. Scenarios must account for user journeys, program specifications, use cases, technical specifications, and pseudocode.

Once the flow graph is prepared, all the paths the journey might take must be mapped for testing and framed as test cases.

Finally comes the execution phase, where the testing is completed, and any issues are recorded for fixing.

 

2. Techniques

The below-listed techniques are used in black box testing:
Equivalence partitioning: Also known as equivalence class partitioning (ECP), this black box testing technique calls for the input values for the application or system to be classified based on outcome similarity.

This enables testing teams to use only one value from within the class or group for analyzing the outcome rather than having to review all the relevant input values from the group. This technique maintains test coverage, and the amount of rework required and time spent are minimized.

For instance, let’s assume a text field that only accepts numerical inputs between 1950 and 2000 to be tested. Using equivalence partitioning, we can create three sets of groups for testing this field: any number less than 1950, any number between 1950 and 2000, and any number greater than 2000.

The valid class will be any one number between 1950 and 2000, while the other two groups will be invalid classes.

In this example, the testing team has reduced the cases to only three, allowing all possible scenarios to be tested within a few moments.

Boundary value analysis: In this technique, the tester focuses on analyzing both valid and invalid values at the boundaries–or the limits at which the system behavior changes. This technique is popular as many applications exhibit bugs when processing boundary values.

Continuing the above example, let’s say a field that accepts values between 1950 and 2000 is being tested. The tester, using boundary value analysis, will enter the following values during testing: 1949 (1950-1), 1950, 1951 (1950+1), 1999 (2000-1), 2000, and 2001 (2000+1). 

Decision table testing: With this method, the tester detects two outputs for two conditions that are defined by a logical connection, such as:

If

{

(Condition = True)

then output1 ;

}

else output2; /*(condition = False)*/

Based on the above example, the tester will create a decision table with all the probable outcomes.

State transition testing: In this technique, the tester analyzes the various states of the application, which change as per events or conditions that the application is subjected to. Each event triggers a state that is then treated as a scenario to be tested.

This technique is handy for simple scenarios, while more complex scenarios will create complicated transition diagrams and make the technique less effective.

Experience-based testing: Guessing the errors that might arise in the application is a key example of this technique. Here, the testing team leverages its experience around the application’s behavior and its functionalities to find the areas prone to errors.

Examples of guessing based on experience include searching for common errors, such as dividing by zero, handling null values in text fields, and accepting blank inputs where they should not be allowed.

Graph-based testing: All applications are created using objects. This method identifies the objects, and an ‘object graph’ is created. This graph is used to identify all object relationships, write test cases, and test for error discovery.

Comparison testing: Finally, in this technique, independent versions of one application are compared to each other during the testing process.

The below-listed techniques are used in white box testing:
Statement coverage: All statements are at least once executed at the source code level in this white box testing approach. The number of statements executed is recorded.

This technique allows the testing team to analyze the source code and set expectations around what it can and cannot do. It is also reliable for checking code quality and verifying path flow. However, one cannot use it to test false conditions.

This method tests the internal coding and infrastructure of the software. It can be carried out by programmers and is suitable for Drupal specialists.

Decision coverage: In this technique, decision coverage is given to Boolean values, and Boolean expressions’ true and false results are reported.

Control flow statements that create a possibility of two or more outcomes, such as ‘do while’, ‘if’, and ‘case’, are considered as ‘decision points’ in this technique as they can lead to two outcomes: either true or false.

This technique covers all the possible results of every Boolean condition within the code through control flow charts and graphs. However, it can sometimes be difficult to achieve complete coverage due to the existence of complicated expressions.

Branch coverage: This technique covers all branches of the control flow graph. Each decision point condition’s possible true and false outcomes are covered at least once. This method guarantees that the several branches of each decision point are executed successfully.

Numerous methods are available for calculating branch coverage, the most common of which is pathfinding. This method uses the number of executed branch paths to calculate branch coverage. Developers can substitute decision coverage with branch coverage.

Condition coverage: In this technique, the testing team analyzes all the conditional expressions in an application for every possible outcome. All the conditions are tested independently, and all the possible results of every condition are tested at least once. Predicate coverage is another name for this technique

Short summary of black box and white box testing

Black box testing and white box testing are two common approaches used in software testing.

Black box testing focuses on testing the functionality of a software application without considering its internal structure or implementation details. Testers treat the system as a "black box," where they input specific inputs and observe the outputs to determine if the application behaves as expected. This type of testing is primarily concerned with validating user requirements, identifying bugs, and ensuring the application meets the desired specifications.

On the other hand, white box testing, also known as structural or glass box testing, involves examining the internal structure, design, and implementation of the software application. Testers have access to the source code and use it to design test cases that target specific paths, conditions, or branches within the code. The goal is to thoroughly test the application's internal components, identify potential code-level issues, and ensure that the software functions correctly.

Both black box and white box testing are crucial for ensuring software quality. Black box testing focuses on the application's external behavior, while white box testing delves into its internal workings. By combining these two approaches, testers can obtain a more comprehensive understanding of the software's functionality and uncover a wider range of potential issues.

 General steps involved in black box testing.

1. Test Planning: Define the objectives, scope, and test strategy for black box testing. Identify the requirements and functionalities to be tested.

2. Test Case Design: Create test cases based on the identified requirements. Test cases should cover various scenarios, inputs, and expected outputs.

3. Test Environment Setup: Set up the necessary test environment, including hardware, software, and test data.

4. Test Execution: Execute the test cases by providing inputs to the software application and comparing the actual outputs to the expected results.

5. Defect Reporting: Document any deviations from expected behavior as defects or bugs in a defect tracking system. Include all relevant information, such as steps to reproduce the issue and the expected behavior.

6. Defect Retesting: After the defects are fixed, retest the affected areas to ensure the issues have been resolved successfully.

7. Test Closure: Evaluate the overall test coverage, review the test results, and provide a summary report. Analyze the effectiveness of the black box testing process and identify areas for improvement.

The specific steps and the order may vary depending on the project and the testing methodology adopted.

General steps involved in white box testing:

1. Code Analysis: Understand the software application's internal structure and design. Analyze the source code, including functions, classes, and modules.

2. Test Planning: Define the white box testing objectives, scope, and strategy. Identify the specific areas of the code to be tested based on code complexity, criticality, and potential risks.

3. Test Case Design: Create test cases that exercise different paths, conditions, and branches within the code. These test cases should ensure maximum code coverage.

4. Test Environment Setup: Prepare the necessary test environment, which includes configuring the development tools, compilers, debuggers, and any required additional software or hardware.

5. Test Execution: Execute the test cases by stepping through the code line by line, monitoring variable values, and verifying the expected behavior of the code.

6. Code Coverage Analysis: Measure the code coverage achieved by the test cases. This analysis helps ensure that all portions of the code have been tested and that there are no untested areas.

7. Defect Reporting: Document any defects or bugs discovered during white box testing in a defect tracking system. Include detailed information about the issue, such as the problematic code snippet, steps to reproduce, and expected behavior.

8. Defect Retesting: After the defects are fixed, retest the affected areas to ensure successful resolution.

9. Test Closure: Evaluate the overall test coverage achieved, review the test results, and provide a summary report. Analyze the effectiveness of the white box testing process and identify areas for improvement.

The specific steps and techniques may vary depending on the programming language, development tools, and testing methodology.

Types of white box texting.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/tsq00y3fnkxur3lx81mq.jpg)

Types of black box tesing


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/zpi63ypgsuk7w3fy6cxi.jpg)

Finally, easy summary table about white box and black box testing.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/xqxkcn0s4gaz7e8dc6t5.jpg)

References

White box testing and black box testing are two different approaches to software testing. Here are some refrences that provide more information about this concept.

1. "White Box Testing vs Black Box Testing: Understanding the Differences" by Guru99: This article explains the differences between white box and black box testing, including their objectives, techniques, advantages, and disadvantages. You can find it at: https://www.guru99.com/white-box-testing-vs-black-box-testing.html

2. "White Box Testing and Black Box Testing Techniques and Tools" by Software Testing Help: This comprehensive guide provides an overview of white box and black box testing, along with various techniques and tools used in each approach. You can access it here: https://www.softwaretestinghelp.com/white-box-testing-and-black-box-testing/

3. "White Box Testing and Black Box Testing" by TechTarget: This resource offers a detailed explanation of white box and black box testing, their purposes, methodologies, and the differences between them. You can read it at: https://searchsoftwarequality.techtarget.com/definition/white-box-testing-and-black-box-testing

4. "Introduction to Software Testing" by edX: This online course covers various aspects of software testing, including white box and black box testing. It provides an in-depth understanding of both approaches and their applications in real-world scenarios. You can enroll in the course here: https://www.edx.org/professional-certificate/introduction-to-software-testing

These references should help you gain a deeper understanding of white box and black box testing and their respective techniques and methodologies.