Mockito Exception - when() requires an argument which has to be a method call on a mock

Question

I have a very simple test case that is using Mockito and Spring Test framework. When I do

when(pcUserService.read("1")).thenReturn(pcUser);

I get this exception.

org.mockito.exceptions.misusing.MissingMethodInvocationException: 
when() requires an argument which has to be 'a method call on a mock'.
For example:
    when(mock.getArticles()).thenReturn(articles);

Also, this error might show up because:
1. you stub either of: final/private/equals()/hashCode() methods.
   Those methods *cannot* be stubbed/verified.
2. inside when() you don't call method on mock but on some other object.

    at com.project.cleaner.controller.test.PcUserControllerTest.shouldGetPcUser(PcUserControllerTest.java:93)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)

I have tried with different methods but keep on getting this error message. I am using Spring 3.1.0.RELEASE with Mockito. Please share and guide me in the right direction.

Answer 1

You need to create a MOCK of pcUserService first, and then use that mock.

PcUserService mock = org.mockito.Mockito.mock(PcUserService.class);
when(mock.read("1")).thenReturn(pcUser);

Answer 2

In case others hit this issue....

It could also be the case that the method you are trying to mock out,pcUserService.read, is declared as a final method. From what I've noticed this appears to cause issues with Mockito.

Answer 3

If you use Kotlin, you should know that methods are final by default. So write open fun instead of fun. Thanks to @djkelly99 for a tip.

Answer 4

Another solution to this issue might be that in case of a test class that is using PowerMockRunner, you might have to add the class that you are mocking to the list, in @PrepareForTest annotation.

For instance -

@PrepareForTest({ PcUserService.class })

Answer 5

I had the same issue, the method that I was trying to mock it was a final method. I removed the modifier and it worked fine.

Answer 6

There's another possible reason for such error - sometimes IDE prefers to statically import Mockito.when() from another package:

import static io.codearte.catchexception.shade.mockito.Mockito.when;

vs

import static org.mockito.Mockito.when; //should normally use this one

The thing is 'when' from io.codearte package is compliant with org.mockito.Mockito.any() on compilation level, but fails during runtime with that exact same error message.