Cannot mock final Kotlin class using Mockito 2

user_1618135 0
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I am unable to mock a Kotlin final class using Mockito 2. I am using Robolectric in addition.

This is my test code:

@RunWith(RobolectricTestRunner.class)
@Config(constants = BuildConfig.class, sdk = 21)
public class Test {

    // more mocks

    @Mock
    MyKotlinLoader kotlinLoader;

    @Before
    public void setUp() {
        MockitoAnnotations.initMocks(this);
    }
}

The test fails when we try to initialise the mocks in the setUp() method.

In addition, I am using the following gradle dependencies in my code:

testCompile 'org.robolectric:robolectric:3.3.2'
testCompile 'org.robolectric:shadows-multidex:3.3.2'
testCompile 'org.robolectric:shadows-support-v4:3.3.2'
testCompile("org.powermock:powermock-api-mockito2:1.7.0") {
    exclude module: 'hamcrest-core'
    exclude module: 'objenesis'
}
testCompile 'junit:junit:4.12'
testCompile 'org.mockito:mockito-inline:2.8.9'

All other unit tests pass using this configuration but as soon as I try to mock the Kotlin class it throws the following error:

Mockito cannot mock/spy because : - final class

Please note I am using Mockito version 2 and I am using the inline dependency which automatically enables the ability to mock final classes.

kotlin mockito unit-testing android java
7 Answers

Since Mockito 2.1.0 there is a possibility to mock final types, enums, and final methods. It was already mentioned in the comments to the original question.

To do this, you’ll need to create a folder (if dont exist) test/resources/mockito-extensions and add there file with the name org.mockito.plugins.MockMaker and this line:

mock-maker-inline

enter image description here

Links to documentation and tutorial

user_13076900

Try adding this below dependency to your build.gradle.

testImplementation 'org.mockito:mockito-inline:2.8.47'

Replace with your mockito version instead of 2.8.47. This will help you to avoid using powermock for the issue.

please look into the below link to know how this thing works.

How to mock a final class with mockito

user_26077380

mock-maker-inline works as is pointed out in other answers. But It's really slow. You can use the all-open plugin to avoid this problem.

To do so you need:

  1. Create an Annotation:
annotation class Mockable
  1. Activate all-open in your build.gradle file:
dependencies {
  classpath "org.jetbrains.kotlin:kotlin-allopen:$kotlin_version"
}

apply plugin: 'kotlin-allopen'

allOpen {
  annotation('com.example.Mockable')
}
  1. Annotate the classes that you want to mock:
@Mockable
class Foo {
  fun calculateTheFoo(): Int {
    sleep(1_000) // Difficult things here
    return 1
  }
}

If you want more information you can read my blog post where I explain this with more details: Mocking Kotlin classes with Mockito — the fast way

user_8426970

Because in kotlin all classes are final by default.

You should also consider adding open to the class declaration.

Example: open class MyClasss{}

user_73387590
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