White Box Testing
With white-box testing, the code under test is known, and we can use what we know about the code and the paths through the code to guide our tests. Additionally, our test cases and knowledge about the code can help guide us to the code locations likely to contain errors. White box testing techniques allow the tester to1: 1) exercise independent paths within the source code; 2) exercise logical decisions as both true and false; and 3) exercise loops at their boundaries. Later classes in the CSC curriculum at NCSU will provide instruction on using white-box testing to test internal data structures.
Typically, when performing white box testing, you want to focus on testing individual methods. This type of testing is called unit testing. Unit testing means that we are testing a specific unit of code, in our case, individual methods. When we start testing methods together, for example when one method calls another method, we are running integration tests. Integration testing means that we are testing how units of code work together. A combination of unit and integration testing can increase the confidence that small portions of our code work together. If the small portions work together, then it is more likely the full system will work correctly.
The test strategies discussed for black box testing (e.g., test requirements, test equivalence classes, and test boundaries) still apply for white box testing. The focus of the test is shifted from the entire program to a method or small unit of our code. With white box testing, we can consider another testing strategy: basis set testing. Since we know the code under test, we can write test cases to exercise all paths in the code. We will write white box tests using each of these strategies.
First, we will discuss how to structure our white box tests so that we
may automate their execution. JUnit is a software testing framework for the Java programming language that reduces the complexity of implementing white-box test cases for your code.
References
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Pressman, R. S. (2005). Software Engineering: A Practitioner’s Approach (6th ed.). McGraw-Hill. ↩