Tasty mocking framework for unit tests in Java

Mockito

Build Status Coverage Status MIT License

Maven Central

Project status

Please see the release notes page.

Updates are announced via Twitter and mailing list Google Groups.

Mockito downloads and instructions for setting up Maven, Gradle and other build systems are available from the Central Repository.

The documentation for all versions is available on javadoc.io (the site is updated within 24 hours of the latest release).

Still on Mockito 1.x? See what’s new in Mockito 2! Mockito 3.x requires Java 8, but otherwise doesn’t introduce any breaking changes compared to the 2.x series.

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Contributions welcome

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Why drink it?

Mockito is a mocking framework that tastes really good. It lets you write beautiful tests with a clean & simple API. Mockito doesn’t give you hangover because the tests are very readable and they produce clean verification errors. Read more about features & motivations.

  • Massive StackOverflow community voted Mockito the best mocking framework for java. Even though StackOverflow shuns questions that likely raise emotional debates the fact is Mockito has the most votes.

  • Top 10 Java library across all libraries, not only the testing tools. In late 2013 there was an analysis made of 30.000 GitHub projects. Although Mockito reached number 9 in the main report, mockito-core and mockito-all are the same tool and therefore the factual position of Mockito is number 4, surpassing famous tools like Guava or Spring. Treat this study as an indicator of a big impact that Mockito makes every day on unit tests written in Java.

  • Dan North, the originator of Behavior-Driven Development wrote this back in 2008:

    “We decided during the main conference that we should use JUnit 4 and Mockito because we think they are the future of TDD and mocking in Java”

    Given the current popularity of Mockito, Dan was spot on with his prediction.

Use your own judgement in choosing a testing framework. The Mockito team always respects your choice. Keep writing great tests every day!

How do I drink it?

Recommended way of getting Mockito is declaring a dependency on “mockito-core” library using your favorite build system. With Gradle one can do:

repositories { mavenCentral() }
dependencies { testImplementation "org.mockito:mockito-core:3.+" }

Maven users can declare a dependency on mockito-core. Mockito publishes every change as a -SNAPSHOT version to a public Sonatype repository.

Users doing manual dependency management can download the jars directly from Maven Central.

Legacy builds with manual dependency management can use the 1.* “mockito-all” distribution. Said distribution has been discontinued in Mockito 2.*.

now you can verify interactions

import static org.mockito.Mockito.*;

// mock creation
List mockedList = mock(List.class);
// or even simpler with Mockito 4.10.0+
// List mockedList = mock();

// using mock object - it does not throw any "unexpected interaction" exception
mockedList.add("one");
mockedList.clear();

// selective, explicit, highly readable verification
verify(mockedList).add("one");
verify(mockedList).clear();

and stub method calls

// you can mock concrete classes, not only interfaces
LinkedList mockedList = mock(LinkedList.class);
// or even simpler with Mockito 4.10.0+
// LinkedList mockedList = mock();

// stubbing appears before the actual execution
when(mockedList.get(0)).thenReturn("first");

// the following prints "first"
System.out.println(mockedList.get(0));

// the following prints "null" because get(999) was not stubbed
System.out.println(mockedList.get(999));

More info

Main reference documentation features:

  • mock()/@Mock: create mock
    • optionally specify how it should behave via Answer/MockSettings
    • when()/given() to specify how a mock should behave
    • If the provided answers don’t fit your needs, write one yourself extending the Answer interface
  • spy()/@Spy: partial mocking, real methods are invoked but still can be verified and stubbed
  • @InjectMocks: automatically inject mocks/spies fields annotated with @Spy or @Mock
  • verify(): to check methods were called with given arguments
    • can use flexible argument matching, for example any expression via the any()
    • or capture what arguments were called using @Captor instead
  • Try Behavior-Driven development syntax with BDDMockito
  • Use Mockito on Android, thanks to the team working on dexmaker

Remember

  • Do not mock types you don’t own
  • Don’t mock value objects
  • Don’t mock everything
  • Show love with your tests!

Click here for more documentation and examples. All documentation lives in javadocs so you don’t need to visit that page too often. 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 2008. 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?

Hats down before EasyMock folks for their ideas on beautiful and refactoring-friendly mocking API. First hacks on Mockito were done on top of the EasyMock code.

Currently Mockito is maintained by Szczepan Faber, Brice Dutheil, Rafael Winterhalter, Tim van der Lippe, Marcin Grzejszczak, Marcin Zajączkowski and a small army of contributors. Friends who contributed to Mockito (apologize if I missed somebody): Pascal Schumacher, Christian Schwartz, Igor Czechowski, Patric Fornasier, Jim Barritt, Felix Leipold, Liz Keogh, Dan North, Bartosz Bańkowski, David Wallace.

GitHub actions and Shipkit are used to facilitate continuous delivery. Both tools are great. Thank you GitHub, thank you Shipkit!

  • Thanks to Éric Lefevre-Ardant for his long running and continuous support on the mailing-list
  • Thanks to Erik Ramfelt, and Steve Christou for the Jenkins server that was used originally for CI.
  • Thanks to Erik Brakkee who originally helped with maven central syncing.
  • Thanks to Igor Czechowski for dealing with maven central and for the name “Mockito”!
  • Thanks to Karol Poźniak for the original colorful logo, Darek Chrzan for the second one, and Évy Dutheil for the third :)

Training by core engineers

Mockito core engineers, experts in the field of software quality can help you with:

  • getting your team up to speed with test automation with mock objects
  • enabling and sustaining test driven development in its best form: BDD
  • achieving maintainable, high quality tests that unlock continuous delivery
  • securing production code quality and minimizing defects through rigorous test automation

Get in touch at [email protected]

Mockito is open source — Want to contribute? — Issue tracker — Mailing list — Training offering