viewModel.onDownloadErrorLiveData.observe(this, { consumable ->
           some code
        })

internal fun graphView(viewGroup: ViewGroup, orientation: graphOrientaion = GraphOrientaion.HORIZONTAL): View {
    return when (orientation) {
        GraphOrientaion.HORIZONTAL -> {
            LayoutInflater.from(viewGroup.context).inflate(R.layout.horizaontal_layout, viewGroup, false)
        }
        GraphOrientaion.VERTICAL -> {
            LayoutInflater.from(viewGroup.context).inflate(R.layout.vertical_layout, viewGroup, false)
        }
    }
}

@Test
fun `graphView - HORIZONTAL view`() {
    val mockOrientation = GraphOrientaion.HORIZONTAL
    every {
        LayoutInflater.from(mockContext).inflate(
            R.layout.horizaontal_layout,
            mockViewGroup,
            false
        )
    } returns mockView
    // EXECUTION
    val view = graphView(mockViewGroup, mockOrientation)
    // VERIFICATION
    assertEquals(mockView, view)
}

java.lang.NullPointerException

at com.vivek$graphView - HORIZONTAL view$1.invoke(TestClass.kt:306)

at com.vivek$graphView - HORIZONTAL view$1.invoke(TestClass.kt:31)

mock.fn()

import io.mockk.every
import io.mockk.mockk
import org.junit.jupiter.api.BeforeEach
import org.junit.jupiter.api.Test
import org.springframework.data.jpa.repository.JpaRepository
import org.springframework.stereotype.Repository
import javax.persistence.Entity
import javax.persistence.Id

@Entity
data class FooEntity(@Id val id: Long)

@Repository
interface FooRepository : JpaRepository<FooEntity, Long>

class Footest {

    private val fooRepository = mockk<FooRepository>()

    @BeforeEach
    fun setUp() {
        every { fooRepository.save(any()) } throws RuntimeException()
    }

    @Test
    fun test() {
        val fooEntity = FooEntity(4321)
        print(fooEntity.id)
    }
}

TimeZone.currentSystemDefault()

java.lang.NoClassDefFoundError: kotlinx/serialization/KSerializer

mockkObject(TimeZone)

class MyTest {
    @Before
    fun setup() {
        mockkObject(TimeZone)
    }

    @After
    fun tearDown() {
        unmockkAll()
    }

    @Test
    fun test() {
        every {
            TimeZone.currentSystemDefault()
        } returns TimeZone.of("Asia/Tokyo")

        assertEquals(TimeZone.currentSystemDefault(), TimeZone.of("Asia/Tokyo"))
    }
}

Aug 20, 2021 7:43:20 PM io.mockk.impl.log.JULLogger warn
WARNING: Failed to transform class kotlinx/datetime/TimeZone$Companion
java.lang.NoClassDefFoundError: kotlinx/serialization/KSerializer
	at java.lang.Class.getDeclaredMethods0(Native Method)
	at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
	at java.lang.Class.getDeclaredMethods(Class.java:1975)
...

Intent

mockk()

mockkConstructor(Intent::class) {
  every { 
    anyConstructed<Intent>().setDataAndType(any(), any())
  } answers { 
    TODO("return same Intent") 
  }
}

object Singleton {
  val client = SomeClient()
   fun foo() {
    // calls to me are mocked in my unit test
    client.bar()
  }
}

foo

mockkObject

every

mockkObject(S3)
every { uploadObject(any(), any(), any()) } returns Unit

S3.uploadObject()

object S3 {
  // some content
  fun uploadObject(stream: InputStream, key: String, metadata: ObjectMetadata): Unit {}
}

every { mockObj.methodXYZ() } returns "..."

every

every

<dependency>
    <groupId>io.mockk</groupId>
    <artifactId>mockk</artifactId>
    <version>1.12.0</version>
    <scope>test</scope>
</dependency>

@file:JvmName

mockkStatic("<jvm-name>")

implementation("io.mockk:mockk-common:1.2.0")

> Could not resolve all files for configuration ':shared:debugUnitTestRuntimeClasspath'.
   > Could not find io.mockk:mockk-common:1.2.0.

any<File>().outputStream()

val mockOs = mockk<FileOutputStream>()
mockkStatic("kotlin.io.FilesKt__FileReadWriteKt")
mockkStatic(Files::class)
val resultFile = mockk<File>()
every { resultFile.path } answers {"somepath"}
every { any<File>().outputStream() } returns mockOs

(No such file or directory)
java.io.FileNotFoundException:  (No such file or directory)
	at java.base/java.io.FileOutputStream.open0(Native Method)
	at java.base/java.io.FileOutputStream.open(FileOutputStream.java:298)
	at java.base/java.io.FileOutputStream.<init>(FileOutputStream.java:237)
	at java.base/java.io.FileOutputStream.<init>(FileOutputStream.java:187)

val time = item.time?.substring(0, 10)

MockK

Jacoco

Maven

@Mockk

0.8.3

0.8.4

0.8.7

MockKAnnotations.init(this)

package mock

import io.mockk.mockk

internal class DummyDatabaseTest {
    val mockConnection: DummyJdbiConnection = mockk()

    every { mockConnection.status() } returns "This is JDBI conncetion"
}

build.gradle

dependencies {
    implementation 'org.jetbrains.kotlin:kotlin-stdlib:1.5.31'

    testImplementation 'org.junit.jupiter:junit-jupiter:5.8.1'
    testImplementation 'org.junit.jupiter:junit-jupiter-params:5.8.1'
    testImplementation 'io.kotest:kotest-assertions-core:4.6.3'
    testImplementation 'io.mockk:mockk:1.12.0'
}

@Primary

@Cacheable

@MockK

MockkAnnotations.init(this, relaxed = true)

mockkStatic

AppCompatDelegate

private fun testTheme(themeMode: Int, radioButtonId: Int) {
    System.out.println("Testing theme: $themeMode")
    selectedTheme = slot()
    every {
        setDefaultNightMode(capture(selectedTheme))
    } answers {
        System.out.println("Setting theme: ${selectedTheme.captured}")
    }

    onView(withId(radioButtonId)).perform(ViewActions.click())

    assertEquals(themeMode, selectedTheme.captured, "Selected theme")
    assertEquals(themeMode, selectedMode, "SharedPreferences")
}

public static final int MODE_NIGHT_FOLLOW_SYSTEM = -1;

public static final int MODE_NIGHT_NO = 1;

public static final int MODE_NIGHT_YES = 2;

RadioButton

@Test
fun `test clicking on light radio button applies light theme`() {
    initialize {
        testTheme(MODE_NIGHT_NO, R.id.fragment_theme_selection_radio_button_light)
    }
}

@Test
fun `test clicking on dark radio button applies dark theme`() {
    initialize {
        testTheme(MODE_NIGHT_YES, R.id.fragment_theme_selection_radio_button_dark)
    }
}

@Test
fun `test clicking on follow system radio button applies system theme`() {
    initialize {
        testTheme(MODE_NIGHT_FOLLOW_SYSTEM, R.id.fragment_theme_selection_radio_button_system)
    }
}

NIGHT_NO

NIGHT_YES

FOLLOW_SYSTEM

lateinit property captured has not been initialized
kotlin.UninitializedPropertyAccessException: lateinit property captured has not been initialized
	at io.mockk.CapturingSlot.getCaptured(API.kt:2503)

@Test
fun `test clicking on follow system radio button applies system theme`() {
    initialize {
        testTheme(MODE_NIGHT_YES, R.id.fragment_theme_selection_radio_button_dark)
        testTheme(MODE_NIGHT_FOLLOW_SYSTEM, R.id.fragment_theme_selection_radio_button_system)
    }
}