Kotlin + MockIto + Android Instrumentation Test

Question

I am trying to run an Instrumentation test (androidTest) using Mockito in Android with Kotlin.

• I've the core library in my dependencies. 'org.mockito:mockito-core:3.3.3'
• My project is written in Kotlin so I've org.mockito:mockito-inline:3.3.3 to fix the final class issue.
• As I want to run the mocks in Android, I've org.mockito:mockito-android:3.3.3 also in my dependencies.

but am getting below error while compiling the code

More than one file was found with OS independent path 'mockito-extensions/org.mockito.plugins.MockMaker'

Here's a sample test code to reproduce the issue. Run this test as an Instrumentation test. (androidTest).

MainActivityTest

import androidx.test.ext.junit.runners.AndroidJUnit4
import org.junit.Assert.assertEquals
import org.junit.Before
import org.junit.Test
import org.junit.runner.RunWith
import org.mockito.Mock
import org.mockito.Mockito.`when`
import org.mockito.MockitoAnnotations

class Calculator {
    fun add(x: Int, y: Int): Int {
        return x + y
    }
}

@RunWith(AndroidJUnit4::class)
class MainActivityTest {

    @Mock
    lateinit var calculator: Calculator

    @Before
    fun before() {
        MockitoAnnotations.initMocks(this)
    }

    @Test
    fun test() {
        `when`(calculator.add(10, 10)).thenReturn(20)
        assertEquals(calculator.add(10, 10), 20)
    }
}

app/build.gradle

plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'kotlin-android-extensions'
}

android {
    compileSdkVersion 29

    defaultConfig {
        applicationId "com.theapache64.mockitosample"
        minSdkVersion 16
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }

    testOptions {
        unitTests.returnDefaultValues = true
    }
}

dependencies {

    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.2.0'
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'com.google.android.material:material:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'

    testImplementation 'junit:junit:4.13'
    androidTestImplementation 'junit:junit:4.13'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    androidTestImplementation 'org.mockito:mockito-core:3.3.3'
    androidTestImplementation 'org.mockito:mockito-android:3.3.3'
    androidTestImplementation 'org.mockito:mockito-inline:3.3.3'
}

Isn't it possible to run Android instrumentation test using Kotlin with Mockito ?

NOTE: If you think this is a duplicate question, I've searched all over the internet. There are other issues with similar stack-trace, but my case is different.

Any help would be highly appreciated

Answer 1

I had the same issue and solution for me was this answer https://stackoverflow.com/a/41594789/2286422, - i.e. to use dexmaker library, which has dependency to Mockito.

Remove other Mockito androidTestImplementation dependencies and only add below one (you can find the latest version here):

androidTestImplementation 'com.linkedin.dexmaker:dexmaker-mockito:2.28.1'

Note that this solution will only work on devices with Android P or above (official documentation).

Then in actual test I'm using Mockito in following way:

@RunWith(MockitoJUnitRunner::class) // use Mockito runner to be able to use @Mock annotations
class MockitoTest {

    @Mock
    private lateinit var generalPref: GeneralPreferences

    @Before
    fun setup() {
        // make setup
    }

    @After
    @Throws(IOException::class) {
        // make cleanup
    }

    @Test
    fun testUser() {
        val repo: UserLocalRepository =
            UserLocalRepositoryImpl(generalPref) // generalPref is a mock
        val user = repo.getUser()
        Truth.assertThat(user).isNotNull()
    }
}