Argument passed to when() is not a mock! Example of correct stubbing: doThrow(new RuntimeException()).when(mock).someMethod();

Question

When using Mockito in JUnit4, I encounter the error in the title.

My code is shown below

package cn.patest.judgerAutoscalerKotlin

import org.junit.Test
import org.mockito.*

import java.lang.RuntimeException

class CalculateScaleToTest {
    @Mock
    private lateinit var test: cn.patest.judgerAutoscalerKotlin.Test

    private fun mockTest() {
        test = cn.patest.judgerAutoscalerKotlin.Test()
        Mockito.doAnswer { 1 }.`when`(test).test()
    }


    @Test
    fun z() {
        mockTest()
    }
}

package cn.patest.judgerAutoscalerKotlin

class Test() {
    fun test(): Int {
        return 1
    }
}

Error details are shown below:

org.mockito.exceptions.misusing.NotAMockException: Argument passed to when() is not a mock! Example of correct stubbing: doThrow(new RuntimeException()).when(mock).someMethod(); at cn.patest.judgerAutoscalerKotlin.CalculateScaleToTest.mockTest(CalculateScaleToTest.kt:53) at cn.patest.judgerAutoscalerKotlin.CalculateScaleToTest.z(CalculateScaleToTest.kt:61) 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.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.runners.ParentRunner.run(ParentRunner.java:363) at org.junit.runner.JUnitCore.run(JUnitCore.java:137)

I searched with google and found some similar issues but they have different situations from mine.

It will be incredibly easier to use mockk, if you are using kotlin. It saved me days — VolodymyrH
I think you are missing the mockito rule: @Rule public MockitoRule mockitoRule = MockitoJUnit.rule(); (added as a field to your test class). — Arcanefoam
@Arcanefoam I added ` @get:Rule var mockitoRule = MockitoJUnit.rule()` as you suggest. After that, I encounter the same error. — A.Chao

Gerold Broser Gerold Broser · Accepted Answer · 2020-06-11T10:13:44

With:

    test = cn.patest.judgerAutoscalerKotlin.Test()

you create a real object, not a mocked one.

Remove the above line and add:

  @Before
  fun before() {

    MockitoAnnotations.initMocks( this )
  }

Reference:

MockitoAnnotations.initMocks(this) method has to be called to initialize annotated fields.

Note also that mocking the class under test in a real environment doesn't make any sense (in contrast to a MCVE like here).

Argument passed to when() is not a mock! Example of correct stubbing: doThrow(new RuntimeException()).when(mock).someMethod();

1 Answers