See also: Java Tip 106: Static inner classes for fun and profit The inner class would be compiled to ClassToTest$StaticInnerTest. Public static class StaticInnerTest extends TestCase Here is a convoluted example of how this would work: // Import statements and package declarations However, if continuous testing requires this method, it may be a signal that the private methods should be extracted, which could be tested in the traditional, public way.
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class output files, they must remain within the same package as declared in source code If a public method has several steps involved, it can consist of several private methods, which can then be tested individually. There is possible merit in testing private methods of a class, particularly with test-driven development, where you would like to design small tests before you write any code.Ĭreating a test with access to private members and methods can test areas of code which are difficult to target specifically with access only to public methods. However, if you're looking for an alternative to using reflection, and have access to the source you're testing, this will still be an option. Having tried Cem Catikkas' solution using reflection for Java, I'd have to say his was a more elegant solution than I have described here. So my tradeoff involves complicating the JUnits with reflection, rather than compromising my security & SDK. But I don't see one can advocate actually not testing code - your mileage may vary. I understand the idea of only testing the "contract". Want to make them visible to anyone to see just forĪnd need to always work (the obvious exception is reflection which can be used to view even private methods in most cases, when SecurityManager is not configured to prevent this). Just two examples of where I would want to test a private method: That way, you indirectly test what the private methods are doing, and maintain a higher level of agility. What I recommend doing instead is using a code coverage tool such as Cobertura, to ensure that the unit tests you write provide decent coverage of the code in private methods. If you do this repeatedly throughout a project, unit tests then stop being a useful measurement of code health, and start to become a hindrance to development, and an annoyance to the development team. If another developer wants to make a small internal change to the class, which doesn't affect the classes public contract, he/she then has to modify your reflection based test to ensure that it works. What you should be testing is the public contract that the class has with other objects you should never directly test an object's internals. Strictly speaking, you should not be writing unit tests that directly test private methods. I have used reflection to do this for Java in the past, and in my opinion it was a big mistake. The setAccessible(true) is required to play around with privates. TargetClass.getDeclaredMethod(methodName, argClasses) lets you look into private methods. Return method.invoke(targetObject, argObjects) Īnd for fields: Field field = TargetClass.getDeclaredField(fieldName) ġ. Method method = TargetClass.getDeclaredMethod(methodName, argClasses) Of course, you can't change private static final variables through reflection. The following patterns will let you do pretty much anything related to the private methods and fields. Internally we're using helpers to get/set private and private static variables as well as invoke private and private static methods. If you have somewhat of a legacy Java application, and you're not allowed to change the visibility of your methods, the best way to test private methods is to use reflection. No design compromises, no overexposing methods and fields for the sake of tests. This way your code remains type-safe and readable. Direct, *type-safe* access to *all* foo's members Some 10 years later perhaps the best way to test a private method, or any inaccessible member, is via from the Manifold framework.