White box testing, also known as structural testing or code-based testing, is a methodology which ensures and validates a software application’s mechanisms, internal framework, and objects and components. This method of testing not only verifies a code as per the design specifications, but also uncovers an application’s vulnerabilities. It is also known as transparent box, glass box, and clear box testing as it clearly visualizes the software’s internal mechanisms for a software engineering team.
During the white box testing phase, a code is run with preselected input values to validate the preselected output values. If a mismatch is found, it implies that the software application is marred by a bug. This process also involves writing software code stubs and drivers.
Overview of the White Box Software Testing Method
Applicable at the unit, integration, and system levels of a software testing phase, the method of white box software testing tests an application at the source code level. The test cases generated as a result of this testing method are based on design techniques like control flow testing, branch testing, path testing, statement coverage, and decision coverage.
This method of testing is one of the best methods to find the errors in the early stages of software development. By following this method, one can test paths within and between units, and between sub-systems when the system-level test is being pursued.
White Box Testing Techniques: At a Glance
The most important part in the white box testing method is the code coverage analysis which empowers a software engineering team to find the area in a code which is unexecuted by a given set of test case thereby, helping in improving a software application’s quality. There are different techniques which can be used to perform the code coverage analysis. Some of these are:
- Statement Coverage: This technique is used to test every possible statement at least once. Cantata++ is the preferred tool when using this technique.
- Decision Coverage: This includes testing every possible decision condition and other conditional loops at least once. TCAT-PATH, supporting C, C++, and Java applications, is the go-to tool when this technique is followed.
- Condition Coverage: This makes one time code execution mandatory when all the conditions are tested.
- Decision/Condition Coverage: This is a mixed technique which is implemented to test all the Decision / Condition coverage at least once while the code is executed.
- Multiple Condition Coverage: In this type of white box testing technique, each entry point of a system has to be executed at least once.
What is Verified in White Box Testing
- Security holes, broken or incomplete paths, and conditional loops in a code
- Flow of structure mentioned in the specification document
- Expected outputs
- Line by line or section by section in a code
- Each statement, object and function is tested individually
Advantages / Pros of White Box Testing
- Code optimization by revealing hidden errors
- Transparency of the internal coding structure which is helpful in deriving the type of input data needed to test an application effectively
- Covers all possible paths of a code thereby, empowering a software engineering team to conduct thorough application testing
- Enables programmer to introspect because developers can carefully describe any new implementation
- Test cases can be easily automated
- Gives engineering-based rules to stop testing an application
Disadvantages / Cons of White Box Testing
- A complex and expensive procedure which requires the adroitness of a seasoned professional, expertise in programming and understanding of internal structure of a code
- Updated test script required when the implementation is changing too often
- Exhaustive testing becomes even more complex using the white box testing method if the application is of large size
- Some conditions might be untested as it is not realistic to test every single one
- Necessity to create full range of inputs to test each path and condition make the white box testing method time-consuming
- Defects in the code may not be detected or may be introduced considering the ground rule of analyzing each line by line or path by path.
White box testing is useful for component, integration and system testing and enables identification of errors in code syntax, logic, data flow and conditions.