February 17, 2019

A simple and practical guide to testing and mocking with JMockit. The full implementation of this tutorial can be found on the GitHub project. A blog on JMockit, an open source software licensed under the MIT License. It includes APIs for mocking, faking, and integration testing, and a. We’ll see step by step in very short tutorials that’ll help you start using jmockit. I’ll be trying to keep each one as crisp as possible. If you want.

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Therefore, the ability to isolate the code under test from certain parts of the system is generally useful in all kinds of tests. Then, code under test is exercised. If you got any doubts we’ll discuss. Again we will see how to mock a static method by using the Expectations and MockUp apis.

Automated developer tests can be divided in two broad categories, whether they target individual program “units”, multiple such units working together, or an entire “slice” of the system under test the “SUT”. But this one tutorizl the concepts in a pragmatic way.

The first mechanism involves simply using the new instance obtained from tutoiral recorded constructor expectation, when recording expectations on instance methods. Finally, there is a small faking API aka the “Mockups” APIwhich can be used for the creation and application of fake implementations that avoid the full cost of external components.

The latter is a mammoth process in itself.

For example, the value “test string” could be specified for a String parameter, causing the expectation to match only those invocations with this exact value in the corresponding parameter. This is a great utility if only some methods of a class need to be redefined. Unknown November 10, at 4: What happens when some other internal code calls the same method with some other value? How to add JMockit to an eclipse project?

There are three special fields just for that: Tested takes care of setting up properly initialized objects to be tested, while Mocked applies mocking to a jmickit type. Yes, som of the links dont work http: As a complement to the assertions performed by each test, the mock itself can encode additional assertions.


Here instead of maxTimes, we can use minTimes and times depending of our logical scenario. Automated developer testing and test isolation Testing with mock objects An example.

Now let us dive into the ocean called JMockit. These verification points are the ones numbered 1 – 4 as indicated above. The return type of a delegate method doesn’t have to be the same as the recorded method, although it should be compatible in order to avoid a ClassCastException later. Even though the tutorial is fairly complete, it does not attempt to cover the entire published APIs in detail.


The assignment to result should appear right after the invocation that identifies the recorded expectation, inside an expectation block.

We will look into more of this in this section. Previously, we explained that an expectation recorded on a mocked instance, such as ” abc.

Learn Jmockit Tutorial – How to use it with Code coverage

One of these implementations is defined through an anonymous inner class, which is completely inaccessible except for the use of Reflection from client code. One of the most beautiful things that can be experienced in life is when you return to your blog after a long time to view a comment! The toolkit is provided as a set of artifacts deployed to the Maven Central repository.

Notice that in these two example tests there is no mock field or mock parameter. Check out setUpMock Learn maxTimes and other similar fields. If InputStream was mocked “normally”, the read byte[] method would always be mocked, regardless of the instance on which it is called. Not only will implementation classes already loaded by the JVM get mocked, but also any additional classes that happen to get loaded by the JVM during later test execution. In that case use the NonStrictExpectations class.


For information on using JMockit Coverage with Mavensee the relevant section in that chapter. The second mechanism lets us associate a given mock instance with a recorded constructor expectation, and then use this instance for recording expectations on instance methods which will match invocations on future instances created with a matching constructor invocation.

If you have read the previous “How to”s, you already know the answer – its the Deencapsulation class. Hope this attempt would be helpful to you. Any idea why I’m getting this exception while running above program? It’s only there so that the expectation can be specified.

JMockit – Tutorial

Note that the call abc. To allow a recorded or verified invocation to match a whole set of replayed invocations with different argument values, we can specify flexible argument matching constraints instead of actual argument values. You can ask them in comments section below This is appropriate for most tests, but in some situations we might need to select only certain methods or constructors to be mocked.

Anonymous May 11, at 6: The same is true for verification blocks. There are more “with” methods than shown above. Mocks are most useful in isolated unit tests, but can also be used in integration tests. One last tip before we move onto the MockUp apis.

I am very likely to know the principle of Jmockit.

Mocking provides a mechanism for isolating a class to be tested from some of its dependencies. I did not get which is the main page. The cascaded mock will allow further cascading, so a null reference will never be obtained from methods which return object references except for non-eligible return types Object or String which will return nullor jmokit types which will return a non-mocked empty collection.

That is, we can freely use the anyXyz fields, the withXyz