Unit Test fails with exception.

[KidusMT]

The test fails when I run it with an exception. How can I handle this? Any suggestion, please.
@amitshekhariitbhu

org.mockito.exceptions.misusing.WrongTypeOfReturnValue: 
ObservableJust cannot be returned by doServerLoginApiCall()
doServerLoginApiCall() should return Single
***
If you're unsure why you're getting above error read  @on.
Due to the nature of the syntax above problem might occur because:
1. This exception *might* occur in wrongly written multi-threaded tests.
   Please refer to Mockito FAQ on limitations of concurrency testing.
2. A spy is stubbed using when(spy.foo()).then() syntax. It is safer to stub spies - 
   - with doReturn|Throw() family of methods. More in javadocs for Mockito.spy() method.


	at com.mindorks.framework.mvp.ui.login.LoginPresenterTest.testServerLoginSuccess(LoginPresenterTest.java:78)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.mockito.internal.runners.DefaultInternalRunner$1.run(DefaultInternalRunner.java:68)
	at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:74)
	at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:39)
	at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:161)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)


Process finished with exit code 255

[KidusMT]

you can close this issue, I worked when I changed the original code

 @Test
    public void testServerLoginSuccess() {

        String email = "dummy@gmail.com";
        String password = "password";

        LoginResponse loginResponse = new LoginResponse();

        doReturn(Observable.just(loginResponse))
                .when(mMockDataManager)
                .doServerLoginApiCall(new LoginRequest
                        .ServerLoginRequest(email, password));

        mLoginPresenter.onServerLoginClick(email, password);

        mTestScheduler.triggerActions();

        verify(mMockLoginMvpView).showLoading();
        verify(mMockLoginMvpView).hideLoading();
        verify(mMockLoginMvpView).openMainActivity();
    }

to

@Test
    public void testServerLoginSuccess() {

        String email = "dummy@gmail.com";
        String password = "password";

        LoginResponse loginResponse = new LoginResponse();

        doReturn(Single.just(loginResponse))
                .when(mMockDataManager)
                .doServerLoginApiCall(new LoginRequest
                        .ServerLoginRequest(email, password));

        mLoginPresenter.onServerLoginClick(email, password);

        mTestScheduler.triggerActions();

        verify(mMockLoginMvpView).showLoading();
        verify(mMockLoginMvpView).hideLoading();
        verify(mMockLoginMvpView).openMainActivity();
    }

which is located in the LoginPresenterTest. And the test passed now. It should have been Single, not Observable.