Internally we're using helpers to get/set private and private static variables as well as invoke private and private static methods. 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. The new and old classes are now both simpler than the original class, which is great for me (I need to keep things simple, or I get lost!). object-oriented design, and Jini. It does exactly what you are looking for. Very helpful, Also, it is preferable if your method of testing, Could you explain why would it make class. So yes reflection is a good way to do this and no your design does not need review if you are using reflection for this purpose. @Test, you can use Dp4j to inject reflection in your test methods. bash loop to replace middle of string after a certain character. Announcing the Stacks Editor Beta release! But that just doesn't feel right to me. Creating 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. First, I'll throw this question out: Why do your private members need isolated testing? 7. An corresponding invokeStaticMethod implementation for use with JUnit would throw AssertionFailedError rather than TestFailedException. Lots of helpful one-liners for accessing private methods and private fields. As others have said don't test private methods directly. If private methods are so complex that they need separates tests then it probably needs to be refactored, not more tests thrown at it. Testing private methods should be tested by debugging before running your unit tests on public methods. Old code will be using an empty constructor, and if you ask me, refactored code will look cleaner, and you'll be able to inject necessary values in test without reflection. Now, if I extract the private method out of a method that already works and has good unit test coverage, then those existing unit tests will likely suffice. PrivateAccessor is the class from JUnit Addons that facilates testing private members: http://junit-addons.sourceforge.net/junitx/util/PrivateAccessor.html, 9.PrivilegedAccessor class, which you can use to access private members: http://groups.yahoo.com/group/junit/files/src/PrivilegedAccessor.java, 10. Have an opinion? However, if you don't mind making those particular private methods you want to test package access, you could use approach 2. When I later applied JUnit to the task of writing actual unit tests, as opposed to conformance tests, I found myself wanting to write white box teststests that employ knowledge of the internal implementation of the packages and classes under test. These methods are really only needed in the class in which they reside, and in fact are often only called by one other method. 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. If I want to be sure of my code, I would like to test every piece that the code flow goes through. By placing both source trees in the CLASSPATH, my test classes could access package-level methods and classes in the package under test. Find centralized, trusted content and collaborate around the technologies you use most. So my tradeoff involves complicating the JUnits with reflection, rather than compromising my security & SDK. Use it carefully. There is also setter injection, but I wouldn't recommended using it. The private methods are called by a public method, so the inputs to your public methods should also test private methods that are called by those public methods. Data Imbalance: what would be an ideal number(ratio) of newly added class's data? The ServiceUI A common pattern, in that case, would be to wrap it within an interface, like Callable and then you pass in that interface also in the constructor (with that multiple constructor trick): Mostly all that I wrote looks like it's a dependency injection pattern. In other words, a conformance test is a "black box" test. A counterexample (real) situation where none of these 3 points is valid (as far as I can think): A public method foo() will 1. use a private method bar() and 2. run in an infinite loop. You're mixing "protected" with "friendly." 6.
This answer did not quite satisfy me, because on occasion I really did feel the urge to directly test a private method. Back when I was building Windows applications in C++, for example, I would write a bit of code to test a newly implemented method, then execute that code and watch it execute by stepping through the method under test with the debugger. If the class's design is still flexible, and you've got a complicated private method that you'd like to test separately, I suggest you pull it out into a separate class and test that class separately. As part of the jmockit library, you have access to the Deencapsulation class which makes testing private methods easy: I use this approach all the time. They clearly feel like private methods to me. (Ans such usefull code can be public, too; less usefull protected. I don't agree. Under unit test, the strategy would provide added validation, but in release builds it would be simple passthrough. Not only touching via coverage ; test that the expected result is delivered! @MasterJoe2: the purpose of a fire test is to improve the safety of your building against the risk of fire. If using Spring, ReflectionTestUtils provides some handy tools that help out here with minimal effort. The public method could require significant setup before you reach the line that calls your private method. One day over lunch, Vladimir enlightened me that the java.lang.reflect API included methods that allowed client code to circumvent access protection mechanism of the Java virtual machine. @LorenzoLerate I've been wrestling with this because I'm doing embedded development and I'd like my software to be as small as possible. Is it bad practice to use Reflection in Unit testing? The main disadvantage of this approach is that the test code is far more verbose because it uses the reflection API. Don't sweat the small stuff. so don't write private methods, just create 10 other small classes ? ;), https://github.com/stephanenicolas/boundbox. Yes, using java reflection is also a hack, but only in the test. I tend not to test private methods. Unlike approach 3, you need not add any extra nested class at package access level. The problem is when the implementation is more complicated, like if one public method calls several private methods. A code coverage tool can show you which parts are covered by the test, therefore you can see if your private method is tested. Most of the time, private methods can be most effectively tested via approach 1, indirectly by testing the package-level, protected, and public methods that call them. When I see a private access specifier on a method, it tells me something I like to knowthat this is part of the implementation of the class. In its current state, the answers are highly Java-oriented, and the question was largely focused on the "how", meaning that the later versions erasing Java and generalizing for other languages, and at the end flipping the focus to C++ invalidates far too many of the answers. A protected method can only be accessed by a class whose objects are assignable to the target class (i.e subclasses). 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. This approach actually works just fine, but it does come with a slight cost. Sure. If this cannot be done, then one of the following conditions is true: When I have private methods in a class that are sufficiently complicated that I feel the need to test the private methods directly, that is a code smell: my class is too complicated. But Daniel is not only source of this advice that I have encountered. The point I was trying to make is that there is good reason for some code to be secret, however that shouldn't prevent us from testing it. These private methods are units that can be tested individually. If you are using JDK 1.3 or higher, you can use reflection to subvert How can I use parentheses when there are math parentheses inside? You mentioned different types of problems. Moreover, the main problem I have with this approach is philosophical. details on how to use it, see this test script. Or if it is a complicated private method, that can't be exposed nor transferred to a new class. That's why you test the public method, asserting the expected results of the public method and thereby, the private methods it consumes. This worked fine, but made me feel a bit dirty somehow. +1 to this. editor-in-chief of Artima.com. @AkashVerma: For the same reason you want to do unit tests instead of just a system test? This still left me, however, with the problem of testing private methods. That's the best answer IMO, or as it is usually said, test behaviour, not methods. and functional programming, enterprise systems, big data, and testing. My usual approach to addressing such issues is to tease out a new class that contains the interesting bits.
Well, maybe. I just want to be able to test private utility methods. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The fourth approach to testing private methods was suggested to me by Vladimir R. Bossicard, who wrote JUnit Addons . Artima SuiteRunner is a free open source testing toolkit and JUnit runner: http://www.artima.com/suiterunner/index.html, 4.JUnit FAQ question about testing private methods: http://junit.sourceforge.net/doc/faq/faq.htm#tests_10, 5. Jini Community since its inception. When I asked Daniel about testing private methods, he gently suggested that I test the private methods indirectly by testing the package-access and public methods that call the private ones. I use the junitx.util.PrivateAccessor-package for Java . Personally, I believe you should only test your publicly exposed interfaces (and that includes protected and internal methods). You already mentioned why the private method should be tested. As Peter mentions, unit tests ought to test the interface, not how it is done internally. I didn't like that the caller of PrivilegedAccessor.invokeMethod would always need to handle the three checked exceptions, because I figured the general way to handle any exception would be to let the test fail. How should I test private methods in Java? @ngreen true thx - I was lazy with the word "public". ServiceUI project that produced the ServiceUI API. Daniel Steinberg  showed me the common JUnit technique of using parallel source code trees, which allowed me to place test classes in the same package as the classes under test, but keep them in a different directory. As many above have suggested, a good way is to test them via your public interfaces. Slightly. I looked at both Vladimir Bossicard's junitx.utils.PrivateAccessor and Charlie Hubbard and Prashant Dhotke's PrivilegedAccessor, but decided that neither of them helped me quite the way I wanted. My initial solution was to just make such private methods package access, which allowed me to test them directly with JUnit from the test classes in the same package in the parallel source tree. Instead, for this example I decided to take approach number 4, and use reflection. It seems bad to change the access modifier for a method just to be able to run a test. For example, to set up a mock on a private member without being forced to add an undesirable public setter: Private methods are consumed by public ones. Now about private methods. I checked for the proper behavior myself by observing via the debugger. Just two examples of where I would want to test a private method: I understand the idea of only testing the "contract". It has the ability to ignore the Java security model and access private methods and attributes. It could take a lot of effort to test a small part of the private method through the public method using it.
Is possible to extract the runtime version from WASM file? Exposing sensible internals just for easier testing of various code paths isn't always sensible, so don't follow this device here blindly!