Software testing is a crucial and mandatory part of the software development process. It is essential to ensure that the software being developed meets the required quality standards and functions as intended.
Black box testing and white box testing are two fundamental testing approaches used by software testers to assess the quality and functionality of the software. As you mentioned, black box testing focuses on checking the accuracy of the system without delving into the internal code or implementation details. Testers perform black box testing by examining the software’s external behaviour and evaluating its functionality against specified requirements.
By using black box testing in the software development process, organisations can enhance the software’s reliability, user experience, and overall quality by uncovering issues from a user’s perspective.
Table of ContentsBlack box testing is a software testing technique where the internal workings or code structure of the system being tested are not known to the tester.
In other words, the tester focuses solely on the external behaviour of the software, without having access to its internal source code. The name “black box” comes from the idea that the internal workings are hidden or “boxed” from the tester’s view.
Key characteristics of black box testing include:
Black box testing encompasses several types of testing techniques, each with a specific focus and objective. Some of the main types of black box testing include:
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Black box testing techniques focus on evaluating software from the user’s perspective, without delving into the internal code structure or logic.
1. Equivalence Partitioning: Divides the input data into equivalent partitions, with each partition being regarded the same by the program. Testing one representative from each partition is usually enough to cover all potential scenarios.
Example: For a form that accepts age input between 18 and 65, equivalence partitions might include:
2. Boundary Value Analysis: Tests the bounds of input ranges, as errors frequently arise on the edge of input limits.
Example: For an input field that accepts values from 1 to 100, boundary values would include:
3. Decision Table Testing: A decision table is used to represent and test different combinations of inputs and predicted outcomes. This method is effective for testing systems that involve several conditions and actions.
Example: For a loan application system with conditions like credit score (high/low) and income (above/below threshold), a decision table might include:
| Credit Score | Income | Loan Approved (Y/N) |
|---|---|---|
| High | Above Threshold | Y |
| High | Below Threshold | Y |
| Low | Above Threshold | N |
| Low | Below Threshold | N |
4. State Transition Testing: Tests the system’s behaviour in various states and transitions between them. It ensures that the system functions properly when transitioning from one state to another.
Example: For a user login system, states might include:
Transitions would be:
5. Use Case Testing: Focuses on validating the functionality of the system based on user interactions described in use cases. It ensures that the system meets the requirements of each use case.
Example: For an online shopping application, a use case might be:
6. Error Guessing: Relies on the tester’s experience and intuition to guess where errors might occur based on common mistakes, past experiences, and known problem areas.
Example: For a file upload feature, error guessing might include testing with:
7. All-pair Testing Technique: All-pair testing, also known as pairwise testing, is a combinatorial testing technique that aims to cover all possible pairs of input parameters in a test set.
The purpose is to ensure that every combination of two input parameters is evaluated at least once, which aids in the detection of problems caused by interactions between parameter pairs.
Consider a web application with three input parameters:
With each parameter having two possible values, there are 2 x 2 x 2 = 8 possible combinations if tested exhaustively. However, using all-pair testing, you might only need a subset of combinations to cover all pairs of values.
Possible Test Cases:
These test cases ensure that each pair of input values is tested, such as:
8. Cause-Effect Technique: The Cause-Effect approach, also known as Cause-Effect Graphing, is a black-box testing method that creates test cases based on the relationships between causes (inputs) and effects (outputs).
This technique aids in systematically determining the functional correctness of a system by visualising and analysing the logical linkages between various situations and actions.
Some key concepts here are:
Example:
Consider an online account login system with the following input conditions (causes) and expected outputs (effects):
Causes:
Effects:
Cause-Effect Graph:
Derived Test Cases:
A simple black box testing example for a login functionality of a web application. In this scenario, we will test the login page without having access to the internal code or implementation details.
Test Case Name : Verify successful login with valid credentials.
Expected Result : The user should be successfully logged into the application’s dashboard/homepage.
Test Case Status : PASS (if the user is redirected to the dashboard/homepage)
Test Case Name : Verify unsuccessful login with invalid credentials.
Wait for the application to process the login request.
Expected Resul t: The login attempt should fail, and an appropriate error message (e.g., “Invalid username or password”) should be displayed on the login page.
Test Case Status : PASS (if the error message is displayed)
Black box testing, as a software testing approach, offers several features and benefits that make it an essential part of the software development process. Some key features of black box testing include:
By leveraging these features, black box testing helps organizations deliver high-quality software that meets user expectations and complies with the specified requirements. When combined with other testing approaches, such as white box testing and gray box testing, it provides a comprehensive testing strategy for software development projects.
Advantages of Black Box Testing
Limitations of Black Box Testing
To overcome some of these limitations, organisations often use a combination of black box testing with other testing approaches like white box testing (to assess internal code and logic) and gray box testing (to combine elements of both black and white box testing).
This mixed approach allows for better test coverage and increased software quality assurance.
There are several black box testing tools available that can assist testers in automating and managing the testing process for software applications. These tools help with creating and executing test cases, capturing test results, and generating reports.
Some popular black box testing tools include:
1. Selenium
Selenium is commonly used for black box testing, particularly for web applications. Selenium is an open-source testing framework that allows testers to automate the testing of web browsers, making it a valuable tool for performing black box testing on web-based systems. It interacts with web elements on the user interface, simulating real user interactions and validating the functionality of the application without accessing its internal code.
2. Appium
Appium is another popular tool that is often used for black box testing, particularly for mobile applications. Appium is an open-source test automation framework that allows testers to automate the testing of native, hybrid, and mobile web applications on both Android and iOS devices. It enables black box testing of mobile apps without accessing the internal code.
Pro Tip :It is advised to perform Selenium and Appium Tests on real device cloud to obtain more accurate test results.
The Cloud Selenium Grid of BrowserStack provides access to over 3000 browser device combinations, enabling QAs to test under actual user conditions for improved performance.
It is simple to test your native and hybrid mobile applications with BrowserStack App Automate and the Appium automation framework . Test on a large number of actual Android and iOS devices.
3. Cypress
Cypress is a powerful test automation framework primarily used for front-end testing, including end-to-end (E2E) testing and user interface (UI) testing. While Cypress is more commonly associated with white box testing due to its ability to access and control the application’s internal code, it can also be used for black box testing to some extent.
While Cypress may provide some black box testing capabilities, its real strength lies in the combination of white box and black box testing. For instance, testers can use Cypress to conduct E2E tests and then complement it with other black box testing techniques like exploratory testing or usability testing .
4. Load Runner
LoadRunner is primarily known as a performance testing tool, and its core focus is on testing the performance, scalability, and reliability of applications under different load conditions. While LoadRunner is not typically used as a dedicated black box testing tool, it can still be employed to perform some aspects of black box testing in specific scenarios, for e.g.
5. SoapUI
SoapUI is primarily known as an API testing tool, and its main focus is on testing the functionality and behavior of APIs (Web services). As such, SoapUI is well-suited for black box testing of APIs, ensuring that they meet the specified requirements without needing access to the underlying code.
Here’s how SoapUI can be used for black box testing of APIs:
For comprehensive black box testing, especially when dealing with end-to-end testing of web applications, it is recommended to use dedicated black box testing tools like Selenium or Cypress in combination with SoapUI for API testing. This combination allows for a more complete testing approach, covering both the functionality of the APIs and the user interface interactions of the application.
Before discussing the difference between Black Box and White Box testing, it is important to understand what Black Box and White Box testing actually is.
White box testing, also known as clear box testing or structural testing, is a software testing approach that involves examining and validating the internal code and logic of a software application.
Testers who perform white box testing have access to the application’s source code and use their knowledge of the code’s structure to design and execute test cases. The goal is to verify the correctness of the code, identify logical errors, and ensure that all code paths and conditions are thoroughly tested.
Grey Box Testing is a software testing technique that blends elements of both black box and white box testing. It involves partial knowledge of the internal workings of the application combined with an emphasis on testing functionality from an end-user perspective.
Testers use this partial insight to design test cases that focus on the integration points and interactions between components, while also validating system behaviour against functional requirements.
Grey Box Testing approach helps identify issues that may arise from both the internal code structure and the external user interface, making it particularly useful for integration and security testing.
The core difference between black box, white box, and grey box testing can be seen in the table below:
| Parameter | Black Box | White Box | Grey Box |
|---|---|---|---|
| Definition | Testing without knowledge of the internal code structure; focuses on inputs and outputs. | Testing with knowledge of the internal code structure; focuses on logic, paths, and structures. | A combination of black box and white box testing; involves some knowledge of the internal workings but focuses on functionality. |
| Focus | Functionality and user requirements. | Internal logic, code structure, and pathways. | Functionality and internal design, focusing on both the end-user perspective and internal processes. |
| Knowledge Required | No knowledge of the internal code or system architecture. | Detailed knowledge of the internal code and system architecture. | Partial knowledge of the internal code or architecture. |
| Test Basis | Requirements, specifications, and user scenarios. | Source code, algorithms, and internal logic. | Requirements, specifications, and a partial understanding of the code. |
| Types of Tests | Functional testing, system testing, acceptance testing. | Unit testing, integration testing, and code coverage analysis. | Integration testing, security testing, and system testing. |
| Testing Scope | Broad, focusing on overall system functionality. | Narrower, focusing on specific code paths and logic. | Mid-level, focusing on both functional and structural aspects. |
| Test Design | Test cases derived from functional requirements and user stories. | Test cases derived from code and design documents. | Test cases based on functional requirements and some knowledge of the system’s internal workings. |
| Tools Used | Test management tools, and functional testing tools. | Debuggers, code analysis tools, and unit testing frameworks. | Functional and security testing tools, along with some code analysis tools. |
Grey box testing takes elements from both black box and white box testing to create a more thorough methodology. Below are some common grey box testing techniques:
1. Integration Testing: Concentrates on verifying the interactions of interconnected modules or systems. This technique guarantees that coupled components function as planned and that data flows correctly between them.
For example, testing the interface between a payment gateway and an e-commerce application to ensure that transactions are correctly handled and data is accurately transmitted across systems.
2. Security Testing: Testing the application for vulnerabilities and security problems requires knowledge of potential weaknesses and system design. This aids in identifying security vulnerabilities that could be exploited.
For example, doing penetration testing on a web application to identify vulnerabilities like as SQL injection or cross-site scripting (XSS), while leveraging knowledge of typical attack vectors and system design.
3. Penetration Testing: Simulates assaults on the program to identify security flaws. Controlled attacks are carried out by testers who are familiar with the system’s architecture and its weaknesses.
For example, you can use tools and procedures to test for potential security vulnerabilities, such as poor authentication systems or unsecured data storage.
4. Error Guessing: This technique involves developing test cases based on the tester’s understanding of the system’s probable flaws.
Examples include testing boundary conditions or input combinations that are known to commonly create problems, such as improper data formats or extreme numbers.
5. Fault Injection: Intentionally inserts defects or problems into the system to assess its resilience and error-handling capabilities. This technique assesses how well the system can manage unexpected or incorrect conditions.
Simulating a server failure or network outage to see how the program manages such disruptions and whether it can recover gracefully.
6. Scenario testing involves generating and testing scenarios that include both functional and non-functional features of a system. To validate complicated user interactions and workflows, this approach makes advantage of partial system knowledge.
Example: Testing a multi-step transaction process in an online banking application, such as user authentication, funds transfer, and transaction recording, to ensure that all parts work properly together.
7. Data Flow Testing: Investigates how data flows through the system, with a focus on data entry, processing, and output. It uses partial knowledge of data handling to ensure that data is correctly processed across several components.
For example, test how user data is entered, evaluated, and stored in a database to ensure data integrity throughout the process.
8. Exploratory Testing Combines structured testing with ad hoc exploration, relying on system knowledge to direct exploratory tests. This approach aids in the discovery of issues that would otherwise go undetected in formal test cases.
Exploring various portions of a web application to identify usability flaws or bugs that are not covered by established test cases.
Grey box testing methodologies use a limited understanding of the system’s internal workings to create and perform tests that cover both functional and structural components. This methodology combines insights from black box and white box testing methodologies to assist find integration flaws, security vulnerabilities, and robustness issues.
Advantages
Disadvantages
Effective black box testing requires careful planning, thorough test case design, and meticulous execution. Here are some best practices to ensure successful black box testing:
By following these best practices, testers can conduct thorough and effective black box testing, identifying and resolving defects, and ensuring that the software meets the desired quality standards and user requirements.
White box testing follows the structural testing strategy, while black box testing follows the behavioural testing strategy.
You need appropriate planning, test case design, execution, and result verification for the behavioural approach. It examines the system’s behaviour from the perspective of its consumers. Manual testing is required to adopt this approach.
The structural approach verifies the implementation of every software module. After creating the tests, the test cases must be committed to the source code repository. Automation testing is the most appropriate method for this.
Using the BrowserStack Real Device Cloud , you can effortlessly test your web and app environments. Through Automate and App Automate , test insights and analytics can be readily captured.
