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2.9. JUnit Testing And You

2.9.1. Getting Started

To err is human, to correct is divine.

When writing code we often make mistakes. So it is important that we test our code frequently and often in order to help spot, fix and remove bugs. Thankfully Java comes with a wonderful suite of tools to help test code. In addition to this, various parties develop and release extensions on the standard JUnit suite and release them for students to make use of. One such example is here. Design Considerations

There are a few different approaches to testing code. One is to focus on code coverage. The code coverage approach to testing is fairly easy to understand. If our test cases hit every line of code and produce the expected results then we have a good indication that our code is relatively bug free. For this design we should try to keep our test cases as modular as possible. As such it is generally recommended that for every method in your class you design a test method corresponding to it. Consider a Human class with the methods setName, getName, setWeight, getWeight, walk, jump. There are two sets of getters and setters and two independent methods. Thus it would be wise to create a test method called testName() which tests the getter/setter for name, and a test method called testWeight() which tests the getter/setter for weight. Things a coder might wish to consider when testing these methods could include what happens when you cast a data type to fit inside a setter (i.e. if your weight is represented integers, will the system round as expected or should you regear your data choice). Additionally, be sure to consider any issues that arise from abusing the setter (i.e. negative weight, or giving NULL for the name). As you test your code, try to consider any way in which you can break your program. Finally, we have two methods left untested: The walk and jump methods. In order to keep them modular, simply create two seperate test methods: testJump and testWalk. Meaningful Tests

When writing your test cases it is important not to just run the code with random tests. All the tests should be designed to test common runtime conditions as well as possible edge conditions that may change the behavior. Additionally try to develop test cases that are independent of each other. If a segment of code has already been properly tested, testing the same chunks of code over again will not add anything and will slow down the overall runtime of tests. Remember quality over quantity! More Information

For more information this blog is an excellent resource to read and learn from.

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