Mockito Mock private field initialization

Question

How I can mock a field variable which is being initialized inline  class Test       private Person person   new Person                public void testMethod             person someMethod                         Here I want to mock person someMethod   while testing the Test testMethod   method for which I need to mock initialization of person variable  Any clue  Edit  I m not allowed to modify Person class

User · Answer

Pretty late to the party  but I was struck here and got help from a friend  The thing was not to use PowerMock  This works with the latest version of Mockito  Mockito comes with this org mockito internal util reflection FieldSetter  What it basically does is helps you modify private fields using reflection  This is how you use it   Mock private Person mockedPerson  private Test underTest            Test public void testMethod         FieldSetter setField underTest  underTest getClass   getDeclaredField  quot person quot    mockedPerson                  verify mockedPerson  someMethod       This way you can pass a mock object and then verify it later  Here is the reference

User · Answer

Mockito comes with a helper class to save you some reflection boiler plate code  import org mockito internal util reflection Whitebox           Mock private Person mockedPerson  private Test underTest            Test public void testMethod         Whitebox setInternalState underTest   quot person quot   mockedPerson                 Update  Unfortunately the mockito team decided to remove the class in Mockito 2  So you are back to writing your own reflection boilerplate code  use another library  e g  Apache Commons Lang   or simply pilfer the Whitebox class  it is MIT licensed   Update 2  JUnit 5 comes with its own ReflectionSupport and AnnotationSupport classes that might be useful and save you from pulling in yet another library

User · Answer

Following code can be used to initialize mapper in REST client mock  The mapper field is private and needs to be set during unit test setup    import org mockito internal util reflection FieldSetter   new FieldSetter client  Client class getDeclaredField  mapper    set new Mapper

User · Answer

In case you use Spring Test try org springframework test util ReflectionTestUtils   ReflectionTestUtils setField testObject   person   mockedPerson

User · Answer

Using  Jarda s guide you can define this if you need to set the variable the same value for all tests    Before public void setClientMapper   throws NoSuchFieldException  SecurityException      FieldSetter setField client  client getClass   getDeclaredField  mapper    new Mapper         But beware that setting private values to be different should be handled with care  If they are private are for some reason   Example  I use it  for example  to change the wait time of a sleep in the unit tests  In real examples I want to sleep for 10 seconds but in unit-test I m satisfied if it s immediate  In integration tests you should test the real value

User · Answer

I already found the solution to this problem which I forgot to post here     RunWith PowerMockRunner class   PrepareForTest   Test class    public class SampleTest     Mock Person person    Test public void testPrintName   throws Exception       PowerMockito whenNew Person class  withNoArguments   thenReturn person       Test test  new Test        test testMethod              Key points to this solution are    Running my test cases with PowerMockRunner   RunWith PowerMockRunner class  Instruct Powermock to prepare Test class for manipulation of private fields   PrepareForTest   Test class    And finally mock the constructor for Person class   PowerMockito mockStatic Person class   PowerMockito whenNew Person class  withNoArguments   thenReturn person

[java] Mockito: Mock private field initialization

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