What Does White Box Testing Focus On?
White box testing takes advantage of extensive knowledge of an application’s internals to develop highly-targeted test cases. Examples of tests that might be performed during white box testing include:
- Path Checking: White box testing can be used to explore the various execution paths within an application to ensure that all conditional statements are correct, necessary, and efficient.
- Output Validation: This enumerates the various potential inputs to a function and ensures that each produces the expected result.
- Security Testing: Static code analysis and other white box testing techniques are used to identify potential vulnerabilities within an application and validate that it follows secure development best practices.
- Loop Testing: Tests the loops within an application to ensure that they are correct, efficient, and properly manage the variables within their scope.
- Data Flow Testing: Tracks variables throughout the execution paths of a program to ensure that variables are declared, initialized, used, and properly manipulated.
Types Of White Box Testing
White box testing can be performed for a few different purposes. The three types of white box testing are:
- Unit Testing: Unit testing is designed to ensure that each component or function of an application works properly. This helps to ensure that the application meets design requirements throughout the development process.
- Integration Testing: Integration testing focuses on the interfaces between the various components within an application. Performed after unit testing, it ensures that not only does each component work well in isolation but also that they can work together effectively.
- Regression Testing: Changes can break things within an application. Regression testing ensures that the code still passes existing test cases after functionality or security updates are made to an application.
White Box Testing Techniques
One of the main advantages of white box testing is that it makes it possible to ensure that every aspect of an application is tested. To achieve full code coverage, white box testing can use the following techniques:
- Statement Coverage: Statement coverage testing ensures that every line of code within an application is tested by at least one test case. Statement coverage testing can help to identify if portions of the code are unused or unreachable, which can be caused by programming errors, updates, etc. Identifying this dead code enables developers to fix incorrect conditional statements or remove redundant code to improve application performance and security.
- Branch Coverage: Conditional statements create branches within an application’s execution code as different inputs can follow different execution paths. Branch coverage testing ensures that every branch within an application is covered by unit testing. This ensures that even little-used code paths are properly validated.
- Path Coverage: An execution path describes the sequence of instructions that can be executed from when an application starts to where it terminates. Path coverage testing ensures that every execution path through an application is covered by use cases. This can help to ensure that all execution paths are functional, efficient, and necessary.
Black Box vs White Box vs Gray Box Testing
Black box, white box, and gray boxes are three approaches to testing. Some of the major differences between the three include:
- Available Information: White box testing provides the evaluator with complete knowledge of the target system (source code, documentation, etc.). Black box testing is performed without any internal information, and gray box testing is a mix where the assessor has some information, such as access to design documents but not source code.
- Test Coverage: The varying levels of information available in the different assessments impact their ability to guarantee test coverage. With full access to source code, white box testing can ensure complete coverage while other techniques cannot.
- Time of Analysis: Since white box testing works on source code, it can be applied early in CI/CD pipelines. Gray box and black box testing require a running application, which places it later in the software development lifecycle (SDLC).
- Tool Usage: With access to source code, white box testers can use static code analysis tools to identify vulnerabilities and other issues with an application’s code. Gray and black box testers use dynamic analysis tools, such as a vulnerability scanner, to interact with a running application.
- Tester Mindset: White box evaluators interact with an application’s source code, placing them in a developer-like role. Gray box and black box testers interact with an application as a user would. This enables them to focus more on how an application actually works compared to what it is designed to do.