{"id":35128,"date":"2016-03-25T18:00:10","date_gmt":"2016-03-25T16:00:10","guid":{"rendered":"http:\/\/examples.javacodegeeks.com\/?p=35128"},"modified":"2019-04-09T13:34:17","modified_gmt":"2019-04-09T10:34:17","slug":"mockito-captor-example","status":"publish","type":"post","link":"https:\/\/examples.javacodegeeks.com\/java-development\/core-java\/mockito\/mockito-captor-example\/","title":{"rendered":"Mockito Captor Example"},"content":{"rendered":"

A unit test should test a class in isolation. Side effects from other classes or the system should be eliminated if possible. Mockito lets you write beautiful tests with a clean & simple API. In this example we will learn how to use ArgumentCaptor class\/ Captor annotation of Mockito. Tools and technologies used in this example are Java 1.8, Eclipse Luna 4.4.2<\/p>\n

1. Introduction<\/h2>\n

Mockito is a popular mocking framework which can be used in conjunction with JUnit. Mockito allows us to create and configure mock objects. Using Mockito simplifies the development of tests for classes with external dependencies significantly. We can create the mock objects manually or can use the mocking framewors like Mockito, EasyMock. jMock etc. Mock frameworks allow us to create mock objects at runtime and define their behavior. The classical example for a mock object is a data provider. In production a real database is used, but for testing a mock object simulates the database and ensures that the test conditions are always the same.\n<\/p>\n

2. Creating a project<\/h2>\n

Below are the steps we need to take to create the project.<\/p>\n

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  1. Open Eclipse. Go to File=>New=>Java Project. In the \u2018Project name\u2019 enter \u2018MockitoCaptorExample\u2019.<\/li>\n
  2. Eclipse will create a \u2018src\u2019 folder. Right click on the \u2018src\u2019 folder and choose New=>Package. In the \u2018Name\u2019 text-box enter \u2018com.javacodegeeks\u2019. Click \u2018Finish\u2019.<\/li>\n
  3. Right click on the package and choose New=>Class. Give the class name as MockitoCaptorExample. Click \u2018Finish\u2019. Eclipse will create a default class with the given name.<\/li>\n<\/ol>\n

    2.1 Dependencies<\/h3>\n

    For this example we need the junit and mockito jars. These jars can be downloaded from Maven repository<\/a>. We are using \u2018junit-4.12.jar\u2019 and \u2018mockito-all-1.10.19.jar\u2019. There are the latests (non-beta) versions available as per now. To add these jars in the classpath right click on the project and choose Build Path=>Configure Build Path. The click on the \u2018Add External JARs\u2019 button on the right hand side. Then go to the location where you have downloaded these jars. Then click ok.<\/p>\n

    3. ArgumentCaptor class<\/h2>\n

    ArgumentCaptor<\/code> class is used to capture argument values for further assertions. Mockito verifies argument values in natural java style: by using an equals()<\/code> method. This is also the recommended way of matching arguments because it makes tests clean & simple. In some situations though, it is helpful to assert on certain arguments after the actual verification. For example:<\/p>\n

    ArgumentCaptor<Contact> argument = ArgumentCaptor.forClass(Contact.class);\nverify(mockClass).doSomething(argument.capture());\nassertEquals(\"Meraj\", argument.getValue().getName());\n<\/pre>\n
    It is recommended to use ArgumentCaptor<\/code> with verification but not with stubbing. Using ArgumentCaptor<\/code> with stubbing may decrease test readability because captor is created outside of assert (aka verify or ‘then’) block. Also it may reduce defect localization because if stubbed method was not called then no argument is captured.<\/p>\n
    In a way ArgumentCaptor<\/code> is related to custom argument matchers. Both techniques can be used for making sure certain arguments where passed to mocks. However, ArgumentCaptor<\/code> may be a better fit if:
     
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