How to resolve Unneccessary Stubbing exception

Question

My Code is as below     RunWith MockitoJUnitRunner class  public class MyClass        private static final String code   Test         Mock      private MyClassDAO dao        InjectMocks      private MyClassService Service   new MyClassServiceImpl          Test      public void testDoSearch   throws Exception            final String METHOD NAME   logger getName   concat   testDoSearchEcRcfInspections               CriteriaDTO dto   new CriteriaDTO             dto setCode code            inspectionService searchEcRcfInspections dto            List lt SearchCriteriaDTO gt  summaryList   new ArrayList lt SearchCriteriaDTO gt              inspectionsSummaryList add dto            when dao doSearch dto   thenReturn inspectionsSummaryList    got error in this line          verify dao  doSearchInspections dto                I am getting below exception   org mockito exceptions misusing UnnecessaryStubbingException   Unnecessary stubbings detected in test class  Test Clean  amp  maintainable test code requires zero unnecessary code  Following stubbings are unnecessary  click to navigate to relevant line of code     1  - gt  at service Test testDoSearch Test java 72  Please remove unnecessary stubbings or use  silent  option  More info  javadoc for UnnecessaryStubbingException class    at org mockito internal exceptions Reporter formatUnncessaryStubbingException Reporter java 838    at org mockito internal junit UnnecessaryStubbingsReporter validateUnusedStubs UnnecessaryStubbingsReporter java 34    at org mockito internal runners StrictRunner run StrictRunner java 49    at org mockito junit MockitoJUnitRunner run MockitoJUnitRunner java 103    at org eclipse jdt internal junit4 runner JUnit4TestReference run JUnit4TestReference java 86    at org eclipse jdt internal junit runner TestExecution run TestExecution java 38    at org eclipse jdt internal junit runner RemoteTestRunner runTests RemoteTestRunner java 459    at org eclipse jdt internal junit runner RemoteTestRunner runTests RemoteTestRunner java 675    at org eclipse jdt internal junit runner RemoteTestRunner run RemoteTestRunner java 382    at org eclipse jdt internal junit runner RemoteTestRunner main RemoteTestRunner java 192     Please help me how to resolve

User · Answer

Looking at a part of your stack trace it looks like you are stubbing the dao.doSearch() elsewhere. More like repeatedly creating the stubs of the same method.

Following stubbings are unnecessary (click to navigate to relevant line of code):
  1. -> at service.Test.testDoSearch(Test.java:72)
Please remove unnecessary stubbings or use 'silent' option. More info: javadoc for UnnecessaryStubbingException class.

Consider the below Test Class for example:

@RunWith(MockitoJUnitRunner.class)
public class SomeTest {
    @Mock
    Service1 svc1Mock1;

    @Mock
    Service2 svc2Mock2;

    @InjectMock
    TestClass class;

    //Assume you have many dependencies and you want to set up all the stubs 
    //in one place assuming that all your tests need these stubs.

    //I know that any initialization code for the test can/should be in a 
    //@Before method. Lets assume there is another method just to create 
    //your stubs.

    public void setUpRequiredStubs() {
        when(svc1Mock1.someMethod(any(), any())).thenReturn(something));
        when(svc2Mock2.someOtherMethod(any())).thenReturn(somethingElse);
    }

    @Test
    public void methodUnderTest_StateUnderTest_ExpectedBehavior() {
        // You forget that you defined the stub for svcMock1.someMethod or 
        //thought you could redefine it. Well you cannot. That's going to be 
        //a problem and would throw your UnnecessaryStubbingException.
       when(svc1Mock1.someMethod(any(),any())).thenReturn(anyThing);//ERROR!
       setUpRequiredStubs();
    }
}

I would rather considering refactoring your tests to stub where necessary.

User · Answer

For me neither the  Rule nor the  RunWith MockitoJUnitRunner Silent class  suggestions worked  It was a legacy project where we upgraded to mockito-core 2 23 0    We could get rid of the UnnecessaryStubbingException by using    Mockito lenient   when mockedService getUserById any     thenReturn new User       instead of    when mockedService getUserById any     thenReturn new User       Needless to say that you should rather look at the test code  but we needed to get the stuff compiled and the tests running first of all

User · Answer

Well  In my case Mockito error was telling me to call the actual method after the when or whenever stub  Since we were not invoking the conditions that we just mocked  Mockito was reporting that as unnecessary stubs or code   Here is what it was like when the error was coming     Test fun  should return error when item list is empty for getStockAvailability          doAnswer          Answer lt Void gt    invocation - gt              val callback                   invocation arguments 1  as GetStockApiCallback lt StockResultViewState Idle  StockResultViewState Error gt              callback onApiCallError stockResultViewStateError              null                 whenever stockViewModelTest           getStockAvailability listOf    getStocksApiCallBack      then I just called the actual method mentioned in when statement to mock the method   changes done is as below stockViewModelTest getStockAvailability listOf    getStocksApiCallBack    Test fun  should return error when item list is empty for getStockAvailability          doAnswer          Answer lt Void gt    invocation - gt              val callback                   invocation arguments 1  as GetStockApiCallback lt StockResultViewState Idle  StockResultViewState Error gt              callback onApiCallError stockResultViewStateError              null                 whenever stockViewModelTest           getStockAvailability listOf    getStocksApiCallBack        called the actual method here     stockViewModelTest getStockAvailability listOf    getStocksApiCallBack      it s working now

User · Answer

Replace  RunWith MockitoJUnitRunner class  with  RunWith MockitoJUnitRunner Silent class

User · Answer

Silent is not a solution  You need fix your mock in your test  See official documentation here   Unnecessary stubs are stubbed method calls that were never realized during test execution  see also MockitoHint   example     code under test        String result   translator translate  one            test        when translator translate  one    thenReturn  jeden        lt - stubbing realized during code execution  when translator translate  two    thenReturn  dwa        lt - stubbing never realized        Notice that one of the stubbed methods were never realized in the code under test  during test execution  The stray stubbing might be an oversight of the developer  the artifact of copy-paste or the effect not understanding the test code  Either way  the developer ends up with unnecessary test code  In order to keep the codebase clean  amp  maintainable it is necessary to remove unnecessary code  Otherwise tests are harder to read and reason about   To find out more about detecting unused stubbings see MockitoHint

User · Answer

At first you should check your test logic  Usually there are 3 cases  First  you are mocking wrong method  you made a typo or someone changed tested code so that mocked method is no longer used   Second  your test is failing before this method is called  Third  you logic falls in wrong if switch branch somewhere in the code so that mocked method is no called   If this is first case you always want to change mocked method for the one used in the code  With second and the third it depends  Usually you should just delete this mock if it has no use  But sometimes there are certain cases in parametrized tests  which should take this different path or fail earlier  Then you can split this test into two or more separate ones but that s not always good looking  3 test methods with possibly 3 arguments providers can make you test look unreadable  In that case for JUnit 4 you silent this exception with either    RunWith MockitoJUnitRunner Silent class     annotation or if you are using rule approach   Rule public MockitoRule rule   MockitoJUnit rule   strictness Strictness LENIENT     or  the same behaviour    Rule public MockitoRule rule   MockitoJUnit rule   silent      For JUnit 5 tests you can silent this exception using annotation provided in mockito-junit-jupiter package    ExtendWith MockitoExtension class   MockitoSettings strictness   Strictness LENIENT  class JUnit5MockitoTest

User · Answer

This was already pointed out in this comment  but I think that s too easy to overlook  You may run into an UnnecessaryStubbingException if you simply convert a JUnit 4 test class to a JUnit 5 test class by replacing an existing  Before with  BeforeEach  and if you perform some stubbing in that setup method that is not realized by at least one of the test cases  This Mockito thread has more information on that  basically there is a subtle difference in the test execution between  Before and  BeforeEach  With  Before  it was sufficient if any test case realized the stubbings  with  BeforeEach  all cases would have to  If you don t want to break up the setup of  BeforeEach into many small bits  as the comment cited above rightly points out   there s another option still instead of activating the lenient mode for the whole test class  you can merely make those stubbings in the  BeforeEach method lenient individually using lenient

User · Answer

As others pointed out it is usually the simplest to remove the line that is unnecessarily stubbing a method call  In my case it was in a  BeforeEach and it was relevant most of the time  In the only test where that method was not used I reset the mock  e g   myMock reset    Hope this helps others with the same problem   Note that if there are multiple mocked calls on the same mock this could be inconvenient as well since you ll have to mock all the other methods except the one that isn t called

User · Answer

Replace    RunWith MockitoJUnitRunner class    with    RunWith MockitoJUnitRunner Silent class   or remove  RunWith MockitoJUnitRunner class   or just comment out the unwanted mocking calls  shown as unauthorised stubbing

User · Answer

I had UnnecessaryStubbingException when I tried to use the when methods on a Spy object   Mockito lenient   silenced the exception but the test results were not correct   In case of Spy objects  one has to call the methods directly    ExtendWith MockitoExtension class   RunWith JUnitPlatform class  class ArithmTest         Spy     private Arithm arithm        Test     void testAddition              int res   arithm add 2  5               doReturn 7  when arithm  add 2  5           assertEquals res  7

User · Answer

If you re using this style instead    Rule public MockitoRule rule   MockitoJUnit rule   strictness Strictness STRICT STUBS     replace it with    Rule public MockitoRule rule   MockitoJUnit rule   silent

User · Answer

If you use any   when mocking   you have to relpace  RunWith MockitoJUnitRunner class  with  RunWith MockitoJUnitRunner Silent class

User · Answer

when dao doSearch dto   thenReturn inspectionsSummaryList    got error in this line  verify dao  doSearchInspections dto     The when here configures your mock to do something   However  you donot use this mock in any way anymore after this line  apart from doing a verify    Mockito warns you that the when line therefore is pointless   Perhaps you made a logic error

User · Answer

In case of a large project  it s difficult to fix each of these exceptions  At the same time  using Silent is not advised  I have written a script to remove all the unnecessary stubbings given a list of them   https   gist github com cueo da1ca49e92679ac49f808c7ef594e75b  We just need to copy-paste the mvn output and write the list of these exceptions using regex and let the script take care of the rest

[java] How to resolve Unneccessary Stubbing exception

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