clearInlineMocks not working with MockitoJUnit.rule()

[melihaksoy]

Hi !

I recenlty updated to 2.25.0 to make use of clearInlineMocks but I end up with NotAMockException when I use it in combination with MockitoJUnit.rule().

Eg

class ExampleUnitTest {

    @get:Rule
    val mockitoRule: MockitoRule = MockitoJUnit.rule()

    @Mock
    lateinit var state: MainState

    @After
    fun clearMocks() {
        Mockito.framework().clearInlineMocks()
    }

    @Test
    fun randomTest() {
		state.something
		Mockito.verify(state).something
    }
}

ends up with

org.mockito.exceptions.misusing.NotAMockException: Argument passed to Mockito.mockingDetails() should be a mock, but is an instance of class com.melih.playground.ui.main.state.MainState!

	at org.mockito.internal.junit.JUnitRule$1.evaluate(JUnitRule.java:49)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)

and tests fail.

If I use @RunWith(MockitoJUnitRunner::class) tests pass, but I still get same exception at end of run.

If I remove rule & use MockitoAnnotations.initMocks(this) everything works fine.

[TimvdLippe]

clearInlineMocks (and all Mockito.framework() APIs) are not intended to be used in regular tests. Instead, they are exposed for those frameworks who want to integrate with Mockito (think of Spring Boot for example). What made you want to choose this API?

Also, it seems like you are using Kotlin. Could it be that the Rule doesn't work correctly when used in combination with Kotlin?

[melihaksoy]

From what's new for 2.25.0 & issue 1614 it sounds like something we should use to prevent mockito-inline from leaking, and we're using it in all modules so far.

MockitoJUnit.rule() worked without any problems, we didn't encounter any anything until we added inline mock clearing.

So clearInlineMocks is not for @After of tests with mockito-inline of my Kotlin tests ?

[TimvdLippe]

Could you open a PR with a reproduction test case? Then I can take a look.

[melihaksoy]

Sorry for late response !

Code piece in question is from a fresh project, just added mockito & rule to ExampleUnitTest, nothing else.

[ttanxu]

I have a theory, but I didn't verify that explicitly so I might be wrong. Just to put this theory here to guide folks to a possible solution.

JUnit runs @Before after each rule, and @After before each rule. In this particular case clearInlineMocks() removed internal handlers of all inline mocks, but MockitoJUnit rule still needs to use them which made this exception.

The solution is to wrap clearInlineMocks() in a TestRule as well, and use RuleChain to make sure the order of those 2 rules.

I'll leave it to Mockito team to decide if it should offer more guidance around the use of clearInlineMocks(), or even encapsulate the use of it into MockitoJUnit rule.

[ZacSweers]

Wow, currently experiencing this XKCD comic. Thank you @ttanxu, that resolved our issue.

Worth noting that RuleChain for ordering is discouraged in Junit 4.13+, so using Rule's ordering works instead

// Use Mockito's new strict stubs listener, which fails early on mismatched types.
// This also handles validating mocks and closing them after the test to prevent leaks.
@Rule(order = 0)
@JvmField
val mockitoRule: MockitoRule = MockitoJUnit.rule().strictness(Strictness.STRICT_STUBS)

// This needs to run _after_ mockitoRule is done
// https://github.com/mockito/mockito/issues/1902#issuecomment-727093806
@Rule(order = 1)
@JvmField
internal val clearInlineMocksRule: TestRule = ClearInlineMocksRule()