Kotlin Academy articles 
Check the series of articles "Mocking is not rocket science" at Kt. Academy describing MockK from the very basics of mocking up to description of all advanced features.
Spring support
- springmockk introduced in official Spring Boot Kotlin tutorial
Kotlin version support
From version 1.10.0 MockK does not support Kotlin 1.2.*
Known issues
- PowerMock needs a workaround to run together with MockK #79. (not sure after workaround if it is generally usable or not, please somebody report it)
- Inline functions cannot be mocked: see the discussion on this issue
Table of contents:
- auto-gen TOC: {:toc}
Examples, guides & articles
- Testing Quarkus with Kotlin, JUnit and MockK
- MockK의 흑마술을 파헤치자! (KO)
- Unraveling MockK's black magic / MockKの「黒魔術」を解明する (JP, but readable through chrome translator)
- Unraveling MockK's black magic(EN, translation)
- Mockk Guidebook
- “Kotlin Unit Testing with Mockk” by Marco Cattaneo
- (Video) Use verify in MockK to validate function calls on mocked object
- Testing With MockK paid course on raywenderlich.com
- TDD for Android video tutorial part 1, part 2 by Ryan Kay
- (Video)Android Developer Live Coding #13: Unit Testing with Mockk, Coroutines, Test Driven Development
- MockK: intentions as of Nov 2018
- KotlinConf 2018 - Best Practices for Unit Testing in Kotlin by Philipp Hauer
- kotlin-fullstack-sample uses MockK project covered with tests
- DZone article
- Habrahabr article (RU)
- Mocking in Kotlin with MockK - Yannick De Turck
Japanese guides and articles
Chinese guides and articles
- 用 Kotlin + Mockito 寫單元測試會碰到什麼問題？
- MockK 功能介紹：mockk, every, Annotation, verify
- MockK 功能介紹：Relaxed Mocks, 再談 Verify, Capture
- 如何測試 Static Method, Singleton
Installation
All you need to get started is just to add a dependency to MockK library.
Gradle/maven dependency
| Approach | Instruction |
|---|---|
 |
testImplementation "io.mockk:mockk:{version}" |
| (Kotlin DSL) |
testImplementation("io.mockk:mockk:{version}") |
 |
<dependency>
<groupId>io.mockk</groupId>
<artifactId>mockk</artifactId>
<version>{version}</version>
<scope>test</scope>
</dependency> |
 Unit |
testImplementation "io.mockk:mockk:{version}" |
| Instrumented |
androidTestImplementation "io.mockk:mockk-android:{version}" |
| Common multiplatform | testImplementation "io.mockk:mockk-common:{version}" |
where {version} corresponds to version as below:
- Kotlin 1.3+ and Coroutines 1.0+ Version:
- Kotlin 1.2 Compatible Version:
DSL examples
Simplest example. By default mocks are strict, so you need to provide some behaviour.
val car = mockk<Car>()
every { car.drive(Direction.NORTH) } returns Outcome.OK
car.drive(Direction.NORTH) // returns OK
verify { car.drive(Direction.NORTH) }
confirmVerified(car)
Annotations
You can use annotations to simplify the creation of mock objects:
class TrafficSystem {
lateinit var car1: Car
lateinit var car2: Car
lateinit var car3: Car
}
class CarTest {
@MockK
lateinit var car1: Car
@RelaxedMockK
lateinit var car2: Car
@MockK(relaxUnitFun = true)
lateinit var car3: Car
@SpyK
var car4 = Car()
@InjectMockKs
var trafficSystem = TrafficSystem()
@Before
fun setUp() = MockKAnnotations.init(this, relaxUnitFun = true) // turn relaxUnitFun on for all mocks
@Test
fun calculateAddsValues1() {
// ... use car1, car2, car3 and car4
}
}
Injection first tries to match properties by name, then by class or superclass. Check the lookupType parameter for customization.
Properties are injected even if private is applied. Constructors for injection are selected from the biggest number of arguments to lowest.
@InjectMockKs by default is injecting only lateinit vars or vars that are not assigned. To change this, use overrideValues = true. This would assign the value even if it is already somehow initialized. To inject vals, use injectImmutable = true. For a shorter notation use @OverrideMockKs which does the same as @InjectMockKs by default, but turns these two flags on.
JUnit5
In JUnit5 you can use MockKExtension to initialize your mocks.
@ExtendWith(MockKExtension::class)
class CarTest {
@MockK
lateinit var car1: Car
@RelaxedMockK
lateinit var car2: Car
@MockK(relaxUnitFun = true)
lateinit var car3: Car
@SpyK
var car4 = Car()
@Test
fun calculateAddsValues1() {
// ... use car1, car2, car3 and car4
}
}
Additionally, it adds the possibility to use @MockK and @RelaxedMockK on test function parameters:
@Test
fun calculateAddsValues1(@MockK car1: Car, @RelaxedMockK car2: Car) {
// ... use car1 and car2
}
Spy
Spies allow to mix mocks and real objects.
val car = spyk(Car()) // or spyk<Car>() to call default constructor
car.drive(Direction.NORTH) // returns whatever real function of Car returns
verify { car.drive(Direction.NORTH) }
confirmVerified(car)
Note: the spy object is a copy of a passed object.
Relaxed mock
A relaxed mock is the mock that returns some simple value for all functions. This allows to skip specifying behavior for each case, while still allowing to stub things you need. For reference types, chained mocks are returned.
val car = mockk<Car>(relaxed = true)
car.drive(Direction.NORTH) // returns null
verify { car.drive(Direction.NORTH) }
confirmVerified(car)
Note: relaxed mocking is working badly with generic return types. A class cast exception is usually thrown in this case. Opt for stubbing manually in case of a generic return type.
Workaround:
val func = mockk<() -> Car>(relaxed = true) // in this case invoke function has generic return type
// this line is workaround, without it the relaxed mock would throw a class cast exception on the next line
every { func() } returns Car() // or you can return mockk() for example
func()
Mock relaxed for functions returning Unit
In case you would like Unit returning functions to be relaxed, you can use relaxUnitFun = true as an argument to the mockk function, @MockKannotation or MockKAnnotations.init function.
Function:
mockk<MockCls>(relaxUnitFun = true)
Annotation:
@MockK(relaxUnitFun = true)
lateinit var mock1: RurfMockCls
init {
MockKAnnotations.init(this)
}
MockKAnnotations.init:
@MockK
lateinit var mock2: RurfMockCls
init {
MockKAnnotations.init(this, relaxUnitFun = true)
}
Object mocks
Objects can be transformed to mocks in the following way:
object MockObj {
fun add(a: Int, b: Int) = a + b
}
mockkObject(MockObj) // applies mocking to an Object
assertEquals(3, MockObj.add(1, 2))
every { MockObj.add(1, 2) } returns 55
assertEquals(55, MockObj.add(1, 2))
To revert back, use unmockkAll or unmockkObject:
@Before
fun beforeTests() {
mockkObject(MockObj)
every { MockObj.add(1,2) } returns 55
}
@Test
fun willUseMockBehaviour() {
assertEquals(55, MockObj.add(1,2))
}
@After
fun afterTests() {
unmockkAll()
// or unmockkObject(MockObj)
}
Despite the Kotlin language limits, you can create new instances of objects if required by testing logic:
val newObjectMock = mockk<MockObj>()
Class mock
Sometimes you need a mock of arbitrary class. Use mockkClass in those cases.
val car = mockkClass(Car::class)
every { car.drive(Direction.NORTH) } returns Outcome.OK
car.drive(Direction.NORTH) // returns OK
verify { car.drive(Direction.NORTH) }
Enumeration mocks
Enums can be mocked using mockkObject:
enum class Enumeration(val goodInt: Int) {
CONSTANT(35),
OTHER_CONSTANT(45);
}
mockkObject(Enumeration.CONSTANT)
every { Enumeration.CONSTANT.goodInt } returns 42
assertEquals(42, Enumeration.CONSTANT.goodInt)
Constructor mocks
Sometimes, especially in code you don't own, you need to mock newly created objects. For this purpose, the following constructs are provided:
class MockCls {
fun add(a: Int, b: Int) = a + b
}
mockkConstructor(MockCls::class)
every { anyConstructed<MockCls>().add(1, 2) } returns 4
assertEquals(4, MockCls().add(1, 2)) // note new object is created
verify { anyConstructed<MockCls>().add(1, 2) }
The basic idea is that just after the constructor of the mocked class is executed (any of them), objects become a constructed mock. Mocking behavior of such a mock is connected to the special prototype mock denoted by anyConstructed<MockCls>(). There is one instance per class of such a prototype mock. Call recording also happens to the prototype mock. If no behavior for the function is specified then the original function is executed.
In case a class has more than one constructor, they can be mocked separately:
class MockCls(private val a: Int = 0) {
constructor(x: String) : this(x.toInt())
fun add(b: Int) = a + b
}
mockkConstructor(MockCls::class)
every { constructedWith<MockCls>().add(1) } returns 2
every {
constructedWith<MockCls>(OfTypeMatcher<String>(String::class)).add(2) // Mocks the constructor taking a String
} returns 3
every {
constructedWith<MockCls>(EqMatcher(4)).add(any()) // Mocks the constructor taking an Int
} returns 4
assertEquals(2, MockCls().add(1))
assertEquals(3, MockCls("2").add(2))
assertEquals(4, MockCls(4).add(7))
verify {
constructedWith<MockCls>().add(1)
constructedWith<MockCls>("2").add(2)
constructedWith<MockCls>(EqMatcher(4)).add(7)
}
Note that in this case, a prototype mock is created for every set of argument matchers passed to constructedWith.
Partial argument matching
You can mix both regular arguments and matchers:
val car = mockk<Car>()
every {
car.recordTelemetry(
speed = more(50),
direction = Direction.NORTH, // here eq() is used
lat = any(),
long = any()
)
} returns Outcome.RECORDED
car.recordTelemetry(60, Direction.NORTH, 51.1377382, 17.0257142)
verify { car.recordTelemetry(60, Direction.NORTH, 51.1377382, 17.0257142) }
confirmVerified(car)
Chained calls
You can stub chains of calls:
val car = mockk<Car>()
every { car.door(DoorType.FRONT_LEFT).windowState() } returns WindowState.UP
car.door(DoorType.FRONT_LEFT) // returns chained mock for Door
car.door(DoorType.FRONT_LEFT).windowState() // returns WindowState.UP
verify { car.door(DoorType.FRONT_LEFT).windowState() }
confirmVerified(car)
Note: in case the function's return type is generic then the information about the actual type is gone. To make chained calls work, additional information is required. Most of the time the framework will catch the cast exception and do autohinting. In the case it is explicitly required, use hint before making the next call.
every { obj.op2(1, 2).hint(Int::class).op1(3, 4) } returns 5
Hierarchical mocking
From version 1.9.1 mocks may be chained into hierarchies:
interface AddressBook {
val contacts: List<Contact>
}
interface Contact {
val name: String
val telephone: String
val address: Address
}
interface Address {
val city: String
val zip: String
}
val addressBook = mockk<AddressBook> {
every { contacts } returns listOf(
mockk {
every { name } returns "John"
every { telephone } returns "123-456-789"
every { address.city } returns "New-York"
every { address.zip } returns "123-45"
},
mockk {
every { name } returns "Alex"
every { telephone } returns "789-456-123"
every { address } returns mockk {
every { city } returns "Wroclaw"
every { zip } returns "543-21"
}
}
)
}
Capturing
You can capture an argument to a CapturingSlot or MutableList:
val car = mockk<Car>()
val slot = slot<Double>()
val list = mutableListOf<Double>()
every {
car.recordTelemetry(
speed = capture(slot), // makes mock match call with any value for `speed` and record it in a slot
direction = Direction.NORTH // makes mock and capturing only match calls with specific `direction`. Use `any()` to match calls with any `direction`
)
} answers {
println(slot.captured)
Outcome.RECORDED
}
every {
car.recordTelemetry(
speed = capture(list),
direction = Direction.SOUTH
)
} answers {
println(list)
Outcome.RECORDED
}
car.recordTelemetry(speed = 15, direction = Direction.NORTH) // prints 15
car.recordTelemetry(speed = 16, direction = Direction.SOUTH) // prints 16
verify(exactly = 2) { car.recordTelemetry(speed = or(15, 16), direction = any()) }
confirmVerified(car)
Verification atLeast, atMost or exactly times
You can check the call count with the atLeast, atMost or exactly parameters:
val car = mockk<Car>(relaxed = true)
car.accelerate(fromSpeed = 10, toSpeed = 20)
car.accelerate(fromSpeed = 10, toSpeed = 30)
car.accelerate(fromSpeed = 20, toSpeed = 30)
// all pass
verify(atLeast = 3) { car.accelerate(allAny()) }
verify(atMost = 2) { car.accelerate(fromSpeed = 10, toSpeed = or(20, 30)) }
verify(exactly = 1) { car.accelerate(fromSpeed = 10, toSpeed = 20) }
verify(exactly = 0) { car.accelerate(fromSpeed = 30, toSpeed = 10) } // means no calls were performed
confirmVerified(car)
Verification order
verifyAllverifies that all calls happened without checking their order.verifySequenceverifies that the calls happened in a specified sequence.verifyOrderverifies that calls happened in a specific order.wasNot Calledverifies that the mock or the list of mocks was not called at all.
class MockedClass {
fun sum(a: Int, b: Int) = a + b
}
val obj = mockk<MockedClass>()
val slot = slot<Int>()
every {
obj.sum(any(), capture(slot))
} answers {
1 + firstArg<Int>() + slot.captured
}
obj.sum(1, 2) // returns 4
obj.sum(1, 3) // returns 5
obj.sum(2, 2) // returns 5
verifyAll {
obj.sum(1, 3)
obj.sum(1, 2)
obj.sum(2, 2)
}
verifySequence {
obj.sum(1, 2)
obj.sum(1, 3)
obj.sum(2, 2)
}
verifyOrder {
obj.sum(1, 2)
obj.sum(2, 2)
}
val obj2 = mockk<MockedClass>()
val obj3 = mockk<MockedClass>()
verify {
listOf(obj2, obj3) wasNot Called
}
confirmVerified(obj)
Verification confirmation
To double check that all calls were verified by verify... constructs, you can use confirmVerified:
confirmVerified(mock1, mock2)
It does not make much sense to use it for verifySequence and verifyAll as these verification methods already exhaustively cover all calls with verification.
It will throw an exception in case there are some calls left without verification.
Some calls may be skipped from such confirmation, check the next section for more details.
val car = mockk<Car>()
every { car.drive(Direction.NORTH) } returns Outcome.OK
every { car.drive(Direction.SOUTH) } returns Outcome.OK
car.drive(Direction.NORTH) // returns OK
car.drive(Direction.SOUTH) // returns OK
verify {
car.drive(Direction.SOUTH)
car.drive(Direction.NORTH)
}
confirmVerified(car) // makes sure all calls were covered with verification
Recording exclusions
To exclude some not so important calls from being recorded you can use excludeRecords:
excludeRecords { mock.operation(any(), 5) }
All matching calls will be excluded from recording. This may be useful in case you are using exhaustive verification: verifyAll, verifySequence or confirmVerified.
val car = mockk<Car>()
every { car.drive(Direction.NORTH) } returns Outcome.OK
every { car.drive(Direction.SOUTH) } returns Outcome.OK
excludeRecords { car.drive(Direction.SOUTH) }
car.drive(Direction.NORTH) // returns OK
car.drive(Direction.SOUTH) // returns OK
verify {
car.drive(Direction.NORTH)
}
confirmVerified(car) // car.drive(Direction.SOUTH) was excluded, so confirmation is fine with only car.drive(Direction.NORTH)
Verification timeout
To verify concurrent operations, you can use timeout = xxx:
mockk<MockCls> {
every { sum(1, 2) } returns 4
Thread {
Thread.sleep(2000)
sum(1, 2)
}.start()
verify(timeout = 3000) { sum(1, 2) }
}
This will wait until one of two following states: either verification is passed or timeout is reached.
Returning Unit
If the function is returning Unit you can use the justRun construct:
class MockedClass {
fun sum(a: Int, b: Int): Unit {
println(a + b)
}
}
val obj = mockk<MockedClass>()
justRun { obj.sum(any(), 3) }
obj.sum(1, 1)
obj.sum(1, 2)
obj.sum(1, 3)
verify {
obj.sum(1, 1)
obj.sum(1, 2)
obj.sum(1, 3)
}
Another ways to write justRun { obj.sum(any(), 3) } is:
every { obj.sum(any(), 3) } just Runsevery { obj.sum(any(), 3) } returns Unitevery { obj.sum(any(), 3) } answers { Unit }
Coroutines
To mock coroutines you need to add another dependency to the support library.
| Gradle |
|---|
testImplementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:x.x" |
| Maven |
|---|
<dependency>
<groupId>org.jetbrains.kotlinx</groupId>
<artifactId>kotlinx-coroutines-core</artifactId>
<version>x.x</version>
<scope>test</scope>
</dependency> |
Then you can use coEvery, coVerify, coMatch, coAssert, coRun, coAnswers or coInvoke to mock suspend functions.
val car = mockk<Car>()
coEvery { car.drive(Direction.NORTH) } returns Outcome.OK
car.drive(Direction.NORTH) // returns OK
coVerify { car.drive(Direction.NORTH) }
Extension functions
There are three cases of extension function:
- class wide
- object wide
- module wide
In case of an object or a class, you can mock extension functions just by creating a regular mockk:
data class Obj(val value: Int)
class Ext {
fun Obj.extensionFunc() = value + 5
}
with(mockk<Ext>()) {
every {
Obj(5).extensionFunc()
} returns 11
assertEquals(11, Obj(5).extensionFunc())
verify {
Obj(5).extensionFunc()
}
}
To mock module wide extension functions you need to build mockkStatic(...) with as argument the module's class name. For example "pkg.FileKt" for module File.kt in the pkg package.
data class Obj(val value: Int)
// declared in File.kt ("pkg" package)
fun Obj.extensionFunc() = value + 5
mockkStatic("pkg.FileKt")
every {
Obj(5).extensionFunc()
} returns 11
assertEquals(11, Obj(5).extensionFunc())
verify {
Obj(5).extensionFunc()
}
On jvm environments you can replace the class name with a function reference:
mockkStatic(Obj::extensionFunc)
Note that this will mock the whole pkg.FileKt class, and not just extensionFunc.
This syntax also applies for extension properties:
val Obj.squareValue get() = value * value
mockkStatic(Obj::squareValue)
If @JvmName is used, specify it as a class name.
KHttp.kt:
@file:JvmName("KHttp")
package khttp
// ... KHttp code
Testing code:
mockkStatic("khttp.KHttp")
Sometimes you need to know a little bit more to mock an extension function. For example File.endsWith() extension function has a totally unpredictable classname:
mockkStatic("kotlin.io.FilesKt__UtilsKt")
every { File("abc").endsWith(any<String>()) } returns true
println(File("abc").endsWith("abc"))
This is standard Kotlin behaviour that may be unpredictable. Use Tools -> Kotlin -> Show Kotlin Bytecode or check .class files in JAR archive to detect such names.
Varargs
From version 1.9.1 more extended vararg handling is possible:
interface ClsWithManyMany {
fun manyMany(vararg x: Any): Int
}
val obj = mockk<ClsWithManyMany>()
every { obj.manyMany(5, 6, *varargAll { it == 7 }) } returns 3
println(obj.manyMany(5, 6, 7)) // 3
println(obj.manyMany(5, 6, 7, 7)) // 3
println(obj.manyMany(5, 6, 7, 7, 7)) // 3
every { obj.manyMany(5, 6, *anyVararg(), 7) } returns 4
println(obj.manyMany(5, 6, 1, 7)) // 4
println(obj.manyMany(5, 6, 2, 3, 7)) // 4
println(obj.manyMany(5, 6, 4, 5, 6, 7)) // 4
every { obj.manyMany(5, 6, *varargAny { nArgs > 5 }, 7) } returns 5
println(obj.manyMany(5, 6, 4, 5, 6, 7)) // 5
println(obj.manyMany(5, 6, 4, 5, 6, 7, 7)) // 5
every {
obj.manyMany(5, 6, *varargAny {
if (position < 3) it == 3 else it == 4
}, 7)
} returns 6
println(obj.manyMany(5, 6, 3, 4, 7)) // 6
println(obj.manyMany(5, 6, 3, 4, 4, 7)) // 6
Private functions mocking / dynamic calls
In case you have a need to mock private functions, you can do it via a dynamic call.
class Car {
fun drive() = accelerate()
private fun accelerate() = "going faster"
}
val mock = spyk<Car>(recordPrivateCalls = true)
every { mock["accelerate"]() } returns "going not so fast"
assertEquals("going not so fast", mock.drive())
verifySequence {
mock.drive()
mock["accelerate"]()
}
In case you want private calls to be verified, you should create a spyk with recordPrivateCalls = true
Additionally, a more verbose syntax allows you to get and set properties, combined with the same dynamic calls:
val mock = spyk(Team(), recordPrivateCalls = true)
every { mock getProperty "speed" } returns 33
every { mock setProperty "acceleration" value less(5) } just runs
justRun { mock invokeNoArgs "privateMethod" }
every { mock invoke "openDoor" withArguments listOf("left", "rear") } returns "OK"
verify { mock getProperty "speed" }
verify { mock setProperty "acceleration" value less(5) }
verify { mock invoke "openDoor" withArguments listOf("left", "rear") }
Property backing fields
You can access the backing fields via fieldValue and use value for value being set.
Note: in the examples below, we use propertyType to specify the type of the fieldValue. This is needed because it is possible to capture the type automatically for the getter. Use nullablePropertyType to specify a nullable type.
val mock = spyk(MockCls(), recordPrivateCalls = true)
every { mock.property } answers { fieldValue + 6 }
every { mock.property = any() } propertyType Int::class answers { fieldValue += value }
every { mock getProperty "property" } propertyType Int::class answers { fieldValue + 6 }
every { mock setProperty "property" value any<Int>() } propertyType Int::class answers { fieldValue += value }
every {
mock.property = any()
} propertyType Int::class answers {
fieldValue = value + 1
} andThen {
fieldValue = value - 1
}
Multiple interfaces
Adding additional behaviours via interfaces and stubbing them:
val spy = spyk(System.out, moreInterfaces = *arrayOf(Runnable::class))
spy.println(555)
every {
(spy as Runnable).run()
} answers {
(self as PrintStream).println("Run! Run! Run!")
}
val thread = Thread(spy as Runnable)
thread.start()
thread.join()
Mocking Nothing
Nothing special here. If you have a function returning Nothing:
fun quit(status: Int): Nothing {
exitProcess(status)
}
Then you can for example throw an exception as behaviour:
every { quit(1) } throws Exception("this is a test")
Clearing vs Unmocking
- clear - deletes internal state of objects associated with mock resulting in empty object
- unmock - re-assigns transformation of classes back to original state prior to mock
Matcher extensibility
A very simple way is to create new matchers by attaching a function to MockKMatcherScope or MockKVerificationScope and using the match function:
fun MockKMatcherScope.seqEq(seq: Sequence<String>) = match<Sequence<String>> {
it.toList() == seq.toList()
}
Also, it is possible to create more advanced matchers by implementing the Matcher interface.
Custom matchers
Example of a custom matcher that compares list without order:
@Test
fun test() {
class MockCls {
fun op(a: List<Int>) = a.reversed()
}
val mock = mockk<MockCls>()
every { mock.op(any()) } returns listOf(5, 6, 9)
println(mock.op(listOf(1, 2, 3)))
verify { mock.op(matchListWithoutOrder(3, 2, 1)) }
}
data class ListWithoutOrderMatcher<T>(
val expectedList: List<T>,
val refEq: Boolean
) : Matcher<List<T>> {
val map = buildCountsMap(expectedList, refEq)
override fun match(arg: List<T>?): Boolean {
if (arg == null) return false
return buildCountsMap(arg, refEq) == map
}
private fun buildCountsMap(list: List<T>, ref: Boolean): Map<Any?, Int> {
val map = mutableMapOf<Any?, Int>()
for (item in list) {
val key = when {
item == null -> nullKey
refEq -> InternalPlatform.ref(item)
else -> item
}
map.compute(key, { _, value -> (value ?: 0) + 1 })
}
return map
}
override fun toString() = "matchListWithoutOrder($expectedList)"
@Suppress("UNCHECKED_CAST")
override fun substitute(map: Map<Any, Any>): Matcher<List<T>> {
return copy(expectedList = expectedList.map { map.getOrDefault(it as Any?, it) } as List<T>)
}
companion object {
val nullKey = Any()
}
}
inline fun <reified T : List<E>, E : Any> MockKMatcherScope.matchListWithoutOrder(
vararg items: E,
refEq: Boolean = true
): T = match(ListWithoutOrderMatcher(listOf(*items), refEq))
Settings file
To adjust parameters globally, there is a possibility to specify a few settings in a resource file.
How to use:
- Create a
io/mockk/settings.propertiesfile insrc/main/resources. - Put one of following options:
relaxed=true|false
relaxUnitFun=true|false
recordPrivateCalls=true|false
stackTracesOnVerify=true|false
stackTracesAlignment=left|center
Where stackTracesAlignment determines whether to align the stack traces displayed when showing recorded calls to the center (default) or to the left (more consistent with usual JVM stackTraces).
DSL tables
Here are a few tables to help you master the DSL.
Top level functions
| Function | Description |
|---|---|
mockk<T>(...) |
builds a regular mock |
spyk<T>() |
builds a spy using the default constructor |
spyk(obj) |
builds a spy by copying from obj |
slot |
creates a capturing slot |
every |
starts a stubbing block |
coEvery |
starts a stubbing block for coroutines |
verify |
starts a verification block |
coVerify |
starts a verification block for coroutines |
verifyAll |
starts a verification block that should include all calls |
coVerifyAll |
starts a verification block that should include all calls for coroutines |
verifyOrder |
starts a verification block that checks the order |
coVerifyOrder |
starts a verification block that checks the order for coroutines |
verifySequence |
starts a verification block that checks whether all calls were made in a specified sequence |
coVerifySequence |
starts a verification block that checks whether all calls were made in a specified sequence for coroutines |
excludeRecords |
exclude some calls from being recorded |
confirmVerified |
confirms that all recorded calls were verified |
clearMocks |
clears specified mocks |
registerInstanceFactory |
allows you to redefine the way of instantiation for certain object |
mockkClass |
builds a regular mock by passing the class as parameter |
mockkObject |
makes an object an object mock or clears it if was already transformed |
unmockkObject |
makes an object mock back to a regular object |
mockkStatic |
makes a static mock out of a class or clears it if it was already transformed |
unmockkStatic |
makes a static mock back to a regular class |
clearStaticMockk |
clears a static mock |
mockkConstructor |
makes a constructor mock out of a class or clears it if it was already transformed |
unmockkConstructor |
makes a constructor mock back to a regular class |
clearConstructorMockk |
clears the constructor mock |
unmockkAll |
unmocks object, static and constructor mocks |
clearAllMocks |
clears regular, object, static and constructor mocks |
Matchers
By default, simple arguments are matched using eq()
| Matcher | Description |
|---|---|
any() |
matches any argument |
allAny() |
special matcher that uses any() instead of eq() for matchers that are provided as simple arguments |
isNull() |
checks if the value is null |
isNull(inverse=true) |
checks if the value is not null |
ofType(type) |
checks if the value belongs to the type |
match { it.startsWith("string") } |
matches via the passed predicate |
coMatch { it.startsWith("string") } |
matches via the passed coroutine predicate |
matchNullable { it?.startsWith("string") } |
matches nullable value via the passed predicate |
coMatchNullable { it?.startsWith("string") } |
matches nullable value via the passed coroutine predicate |
eq(value) |
matches if the value is equal to the provided value via the deepEquals function |
eq(value, inverse=true) |
matches if the value is not equal to the provided value via the deepEquals function |
neq(value) |
matches if the value is not equal to the provided value via deepEquals function |
refEq(value) |
matches if the value is equal to the provided value via reference comparison |
refEq(value, inverse=true) |
matches if the value is not equal to the provided value via reference comparison |
nrefEq(value) |
matches if the value is not equal to the provided value via reference comparison |
cmpEq(value) |
matches if the value is equal to the provided value via the compareTo function |
less(value) |
matches if the value is less than the provided value via the compareTo function |
more(value) |
matches if the value is more than the provided value via the compareTo function |
less(value, andEquals=true) |
matches if the value is less than or equal to the provided value via the compareTo function |
more(value, andEquals=true) |
matches if the value is more than or equal to the provided value via the compareTo function |
range(from, to, fromInclusive=true, toInclusive=true) |
matches if the value is in range via the compareTo function |
and(left, right) |
combines two matchers via a logical and |
or(left, right) |
combines two matchers via a logical or |
not(matcher) |
negates the matcher |
capture(slot) |
captures a value to a CapturingSlot |
capture(mutableList) |
captures a value to a list |
captureNullable(mutableList) |
captures a value to a list together with null values |
captureLambda() |
captures a lambda |
captureCoroutine() |
captures a coroutine |
invoke(...) |
calls a matched argument |
coInvoke(...) |
calls a matched argument for a coroutine |
hint(cls) |
hints the next return type in case it's gotten erased |
anyVararg() |
matches any elements in a vararg |
varargAny(matcher) |
matches if any element is matching the matcher |
varargAll(matcher) |
matches if all elements are matching the matcher |
any...Vararg() |
matches any elements in vararg (specific to primitive type) |
varargAny...(matcher) |
matches if any element is matching the matcher (specific to the primitive type) |
varargAll...(matcher) |
matches if all elements are matching the matcher (specific to the primitive type) |
A few special matchers available in verification mode only:
| Matcher | Description |
|---|---|
withArg { code } |
matches any value and allows to execute some code |
withNullableArg { code } |
matches any nullable value and allows to execute some code |
coWithArg { code } |
matches any value and allows to execute some coroutine code |
coWithNullableArg { code } |
matches any nullable value and allows to execute some coroutine code |
Validators
| Validator | Description |
|---|---|
verify { mock.call() } |
Do unordered verification that a call was performed |
verify(inverse=true) { mock.call() } |
Do unordered verification that a call was not performed |
verify(atLeast=n) { mock.call() } |
Do unordered verification that a call was performed at least n times |
verify(atMost=n) { mock.call() } |
Do unordered verification that a call was performed at most n times |
verify(exactly=n) { mock.call() } |
Do unordered verification that a call was performed exactly n times |
verifyAll { mock.call1(); mock.call2() } |
Do unordered verification that only the specified calls were executed for the mentioned mocks |
verifyOrder { mock.call1(); mock.call2() } |
Do verification that the sequence of calls went one after another |
verifySequence { mock.call1(); mock.call2() } |
Do verification that only the specified sequence of calls were executed for the mentioned mocks |
verify { mock wasNot Called } |
Do verification that a mock was not called |
verify { listOf(mock1, mock2) wasNot Called } |
Do verification that a list of mocks were not called |
Answers
An Answer can be followed up by one or more additional answers.
| Answer | Description |
|---|---|
returns value |
specify that the matched call returns a specified value |
returnsMany list |
specify that the matched call returns a value from the list, with subsequent calls returning the next element |
throws ex |
specify that the matched call throws an exception |
answers { code } |
specify that the matched call answers with a code block scoped with answer scope |
coAnswers { code } |
specify that the matched call answers with a coroutine code block with answer scope |
answers answerObj |
specify that the matched call answers with an Answer object |
answers { nothing } |
specify that the matched call answers null |
just Runs |
specify that the matched call is returning Unit (returns null) |
propertyType Class |
specify the type of backing field accessor |
nullablePropertyType Class |
specify the type of backing field accessor as a nullable type |
Additional answer(s)
A next answer is returned on each consequent call and the last value is persisted. So this is similar to the returnsMany semantics.
| Additional answer | Description |
|---|---|
andThen value |
specify that the matched call returns one specified value |
andThenMany list |
specify that the matched call returns value from the list, returning each time next element |
andThenThrows ex |
specify that the matched call throws an exception |
andThen { code } |
specify that the matched call answers with a code block scoped with answer scope |
coAndThen { code } |
specify that the matched call answers with a coroutine code block with answer scope |
andThenAnswer answerObj |
specify that the matched call answers with an Answer object |
andThen { nothing } |
specify that the matched call answers null |
Answer scope
| Parameter | Description |
|---|---|
call |
a call object that consists of an invocation and a matcher |
invocation |
contains information regarding the actual function invoked |
matcher |
contains information regarding the matcher used to match the invocation |
self |
reference to the object invocation made |
method |
reference to the function invocation made |
args |
reference to the arguments of invocation |
nArgs |
number of invocation argument |
arg(n) |
n-th argument |
firstArg() |
first argument |
secondArg() |
second argument |
thirdArg() |
third argument |
lastArg() |
last argument |
captured() |
the last element in the list for convenience when capturing to a list |
lambda<...>().invoke() |
call the captured lambda |
coroutine<...>().coInvoke() |
call the captured coroutine |
nothing |
null value for returning nothing as an answer |
fieldValue |
accessor to the property backing field |
fieldValueAny |
accessor to the property backing field with Any? type |
value |
value being set casted to same type as the property backing field |
valueAny |
value being set with Any? type |
callOriginal |
calls the original function |
Vararg scope
| Parameter | Description |
|---|---|
position |
the position of an argument in vararg array |
nArgs |
overall count of arguments in vararg array |
Funding
You can also support this project by becoming a sponsor. Your logo will show up here with a link to your website.
Sponsors
Backers
Thank you to all our backers!
Contributors
This project exists thanks to all the people who contribute.
Getting Help
To ask questions, please use Stack Overflow or Gitter.
- Chat/Gitter: https://gitter.im/mockk-io/Lobby
- Stack Overflow: http://stackoverflow.com/questions/tagged/mockk
To report bugs, please use the GitHub project.
- Project Page: https://github.com/mockk/mockk
- Reporting Bugs: https://github.com/mockk/mockk/issues
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