Maven users can declare a dependency on mockito-core. Users doing manual dependency management can download the jars directly from Maven Central. Legacy builds with manual dependency management can use the 1.
Said distribution has been discontinued in Mockito 2. Main reference documentation features:. Click here for more documentation and examples. There is also a RefCard. If you have suggestions, find documentation unclear, or find a bug, write to our mailing list. You can report feature requests and bugs in GitHub. Mockito is served to you by Szczepan Faber and friends. First engineers who were using Mockito in production were developers of the Guardian project in London in early Szczepan was lucky to be a part of the ThoughtWorks team assigned to the challenging and exciting Guardian project.
Here is how he explained why we needed another mocking framework? Then, we mock the Entity Manager. This happens with the mock static call. Using an annotation would also work. The most important line of the whole test is the next one. This defines what will happen when somebody calls the find method of the entityManager. We set it up so that our sample customer is returned, i. Finally, we create our class under test CustomerReader and pass it our own mocked Entity Manager as a dependency.
For this particular example, we have added a new setter method to follow setter injection, but this would work with constructor injection as well. From that point on, our class under test does not really know that the Entity Manager is fake. It will just call its method and get the sample Customer unaware that Mockito is behind everything. This test satisfies all requirements outlined in the previous section.
It has no external dependencies, it only needs the Java source code, it is very fast and it is completely deterministic. We did not need a database at all. Using simple stubbing directives when something. Depending on your application, this might be the only Mockito feature you will ever need. If you have multiple test methods, it makes sense to move the mock creation process to a single place and only differentiate its behavior for each individual test.
You might have already noticed that our CustomerReader class is not correct, as it does not handle the null case, i. While we could copy-paste the existing unit test, it is best if we organize the code with a common test method. Here, we have extracted the common code of creating our test class and its mocked dependencies into the setup method. The Before annotation will make this initialization code run for each test method. The only thing that differs between each test method is the when directive.
In the second case, we make the fake database return null to emulate a customer that does not exist in the Database. In true TDD , fashion we have created the unit tests before the actual implementation. If you run our unit test, the second test method will fail. As you are adding more tests, it will be obvious that not having to deal with a real database allows you to iterate faster on each subsequent implementation feature.
This class has two external dependencies, and we use constructor injection this time around. It checks for late invoices of customers and sends them an email if an invoice is late. In a real system, the InvoiceStorage class is actually a web service that connects with an external legacy CRM system which is slow. A unit test could never make use of such a web service. The EmailSender class is also an external system from a third-party mass email provider. So, we will mock it as well.
However, as soon as you try to write a unit test for this class, you will notice that nothing can really be asserted. The method that we want to test — notifyIfLate — is a void method that cannot return anything. So how do we test it? In this case, we need to focus on the side effects of the code. The side effect here is sending an email. This email is sent only if an outstanding invoice is present.
Mockito provides the verify family of directives for testing side-effects. Here is the whole unit test:. For the first test, we assume the customer has an outstanding invoice. For the second test, no late invoice is present. Both tests do not contain the normal JUnit assert statements. Instead, we use the verify directive which examines the mocks after each run and passes the test if a method was called with the specified argument. For the second test, we want to make sure that the email method is NOT called.
Therefore, we also add the times argument to restrict the number of times this method was not called. If times is omitted it is assumed to be 1, which is what we do in the first test. Notice that mocks can still be stubbed if needed.
The previous example was relatively simple, we just verified whether a single method was called or not. Sometimes we need more detail, and instead of looking only at the method call itself, we are also interested in the arguments. The LateInvoiceNotifier class is then augmented with an EventRecorder dependency, and you want to write a unit tests that verify that the event recorded:. Mockito supports the examination of method arguments via the ArgumentCaptor construct.
Here is the source code of the unit test:. The unit test here examines two related actions. First of all, it verifies that the email was indeed sent as in the previous section. For the event, we could also use a second verify directive to check it as well, but instead, we use an ArgumentCaptor to examine the event in more detail.
First, we construct an ArgumentCaptor and define it as a holder for an Event class. Then, in the verify directive we use our captor by calling its capture method.
At this point, when the unit test is complete, the captor contains the exact argument that was sent to the mocked EventRecorder class when the notifyIfLate method was called.
We can extract the actual argument instance by calling the getValue method of the captor. The result is a normal Java object that can be used for further assertions using the usual JUnit statements. In the example above, we check the event type, the fact that the full name is formed correctly, and whether there is a timestamp.
Note that the argument can be any complex Java object. Mockito could capture it without any problem, and you could run any number of assert statements in the final result, or any fields of the argument class. As a final example of the power of Mockito we will see how you can create custom responses from mocks that depend on the arguments of the call. This is an advanced technique that will be needed only for some very specific corner cases in your unit tests.
Use dynamic responses only as a last resort in your unit tests. You should instantly see why writing a unit test for this class is a bit tricky. I haven't yet massaged my description here, but I haven't forgotten about it either.
Show 2 more comments. Jacob Wu Jacob Wu 7 7 silver badges 11 11 bronze badges. Excellent link. The genius behind this is: The very simple API which makes the whole thing looks like very nice. Another great decision is that the when method uses generics so that the thenReturn method is type safe. I consider this the better answer. In contrast to the other answer, it clearly explains the concepts of the mocking process instead of the control flow through concrete code.
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