Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/mockative/mockative

Mocking for Kotlin/Native and Kotlin Multiplatform using the Kotlin Symbol Processing API (KSP)
https://github.com/mockative/mockative

android ios kotlin kotlin-multiplaform kotlin-native kotlin-symbol-processor ksp mock mocking testing

Last synced: 1 day ago
JSON representation

Mocking for Kotlin/Native and Kotlin Multiplatform using the Kotlin Symbol Processing API (KSP)

Awesome Lists containing this project

README 

        
# Mockative



[ksp]: https://github.com/google/ksp



[![Maven Central](https://img.shields.io/maven-central/v/io.mockative/mockative)](https://search.maven.org/artifact/io.mockative/mockative)



> [!IMPORTANT]  

> Mockative 3 now supports Kotlin 2! A new Gradle plugin has been introduced to make mocking much simpler in

> Mockative 3. Please take the time to read through this README if you're upgrading from Mockative 2, and follow the

> [Migrating to Mockative 3](wiki/MIGRATING-TO-3.md) guide for a successful migration.



Mocking for Kotlin/Native and Kotlin Multiplatform using the Kotlin Symbol Processing API ([KSP]).

Notable features include:



- Concise, non-intrusive, type-safe API

- Mocking of classes and interfaces

- Supports both [values](#stubbing-using-values) and [matchers](#stubbing-using-matchers) when

  during stubbing [verification](#verification)

- Supports [implicit stubbing](#implicit-stubbing-of-functions-returning-unit) of functions

  returning `Unit`



## Installation for Multiplatform projects



Add the `io.mockative` plugin and dependency to your **build.gradle.kts** file:



```kotlin

plugins {

  id("io.mockative") version "3.0.1"

}



kotlin {

    commonMain {

        dependencies {

            implementation("io.mockative:mockative:3.0.1")

        }

    }

}

```



Mockative is published to Maven Central and applies the following Gradle plugins:



- `com.google.devtools.ksp`: Enables code generation of mockable implementations

- `org.jetbrains.kotlin.plugin.allopen`: Enables mocking of classes



Make sure you specify the following plugin repositories in your **build.settings.kts** file:



```kotlin

pluginManagement {

    repositories {

        gradlePluginPortal()

        google()

        mavenCentral()

    }

}

```



Then add the following to your **gradle.properties** file:



```properties

#KSP

ksp.useKSP2=true

```



> [!TIP]

> Now run your tests, which will copy a set of runtime dependencies to your generated code. These will disappear

> whenever you run a Gradle task that is not a test, lint of other verification task, but will reappear once you run

> one of them again.



If you're having the following error:



> KSP2: KtInvalidLifetimeOwnerAccessException: Access to invalid KtAlwaysAccessibleLifetimeToken: PSI has changed since

> creation



Please disable incremental processing for KSP by adding the following to your **gradle.properties** file:



```properties

ksp.incremental=false

```



Mockative 3 code generation should "just work", but if you're looking for more control over when Mockative code

generation is enabled or disabled, please

read [Controlling generation of mocks in Mockative 3](wiki/CONTROLLING_MOCKATIVE_3.md).



### Making types mockable



To mock an interface or class with Mockative, annotate the type with the `@Mockable` annotation. This annotation

tells Mockative to generate a mock implementation of the annotated type, which can be used in tests.



```kotlin

import io.mockative.Mockable



@Mockable

class MyService {

    // ...

}

```



The Kotlin `all-open` plugin will automatically be applied to any `class` annotated with `@Mockable`.



#### Mocking External Types



Sometimes we would like to mock types that are external to our module in our tests. To do so, pass a list of types

you'd like to mock in **any** `@Mockable` annotation in your main module. If you add the list of types to the

`@Mockable` annotation of a type you'd also like to mock by itself, you must specify the type itself in the list of

types to mock. By not specifying any types in the annotation, a mock for the annotated type itself is generated.



```kotlin

import io.mockative.Mockable



@Mockable(MyService::class, Clock::class)

class MyService {

    // ...

}

```



## Testing with Mockative



Obtaining an instance of a mock is as ease as calling the ` mock(KClass)` function:



```kotlin

class GitHubServiceTests {

    val api = mock(of())

}

```



Then, to stub a function or property on the mock you have a couple of options:



### Stubbing using values



To begin stubbing a function you may simply pass the values to the function call inside a block

passed to the `every` or `coEvery` (when stubbing a `suspend` function) functions:



```kotlin

// Stub a blocking function

every { githubApi.getRepository("mockative/mockative") }

    .invokes { response }



// Stub a `suspend` function (notice the use of `coEvery`)

coEvery { repositoryMapper.mapResponseToRepository(response) }

    .invokes { repository }



// Stub a property getter

every { repository.maintainer }

    .returns("Nillerr")



// Stub a property setter (these are stubbed by default)

every { repository.stars = repository.stars + 1 }

    .doesNothing()

```



### Stubbing using matchers



Sometimes when stubbing a function we're faced with difficulties providing a specified value for

one or more of the parameters of our expectation. In such cases we can use the matcher API to

specify the values our stub accepts:



```kotlin

// Assuming we want to stub the function in this S3Client:

interface S3Client {

    suspend fun  getObject(input: GetObjectRequest, block: suspend (GetObjectResponse) -> T): T

}



// Providing a value for the `block` parameter is difficult, so we can use the `any()` matcher to

// specify that this expectation will match any value passed to that parameter. When we use one 

// matcher, we must use matchers for every parameter, and as such we must use the `eq(value)` 

// matcher to specify that we're expecting a specific request.

coEvery { s3Client.getObject(eq(request), any()) }

    .returnsMany(expected)

```



Also note how we're explicitly specifying the type parameter. We could do the same by explicitly

specifying it in the call to `any()` like this:



```kotlin

any File>()

```



But that would be significantly more verbose that the alternative.



> âť•Mockative has limited support for the matcher API when targeting Kotlin/Wasm (WASI).



### Stubbing using functions



You may want to provide a function as an argument to another function, where you would like to be

able to record invocations on that function. To do that, Mockative includes the interfaces `Fun[N]`

and `CoFun[N]` (for `suspend` functions), each declaring a single function `invoke` that you can

pass as a mock to other functions in order to stub and verify invocations on it:



```kotlin

// Declare the mock function as a property in your test class

@Mock

val block = mock(of>())



// Stub the mock function

every { block.invoke(response) }

    .returns(file)



// Call something that calls the mock function

s3Client.getObject(request, block::invoke)



// Verify the call to the mock function

verify { block.invoke(response) }

    .wasInvoked(exactly = once)

```



### Stubbing implementations



The following functions are available to provide a stub implementation for every expectation:



| Function                                              | Description                                                                                                                                                                                                                      |

|-------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| `invokes(block: (args: Array) -> R)`            | Invokes the specified block. The arguments passed to the block are the arguments passed to the invocation.                                                                                                                       |

| `invokes(block: () -> R)`                             | Invokes the specified block.                                                                                                                                                                                                     |

| `invokesMany(vararg block: (args: Array) -> R)` | Invokes the specified blocks in sequence. The arguments passed to the block are the arguments passed to the invocation. Once the last block in the sequence has been invoked, this stubbing will no longer match any invocation. |

| `invokesMany(vararg blocks: () -> R)`                 | Invokes the specified block. Once the last block in the sequence has been invoked, this stubbing will no longer match any invocation.                                                                                            |

| `returns(value: R)`                                   | Returns the specified value.                                                                                                                                                                                                     |

| `returnsMany(vararg value: R)`                        | Returns the specified values in sequence. Once the last value in the sequence has been returned, this stubbing will no longer match any invocation.                                                                              |

| `throws(throwable: Throwable)`                        | Throws the specified exception.                                                                                                                                                                                                  |

| `throwsMany(throwable: Throwable)`                    | Throws the specified exceptions in sequence. Once the last exception in the sequence has been thrown, this stubbing will no longer match any invocation.                                                                         |



In order to provide familiarity to developers coming from MockK, who prefer using infix notation,

Mockative also supports infix notation for the `invokes`, `returns`, and `throws` functions:



```kotlin

every { api.getUsers() } returns users

```



When the return type of the function or property being stubbed is `Unit`, the following additional

then function is available:



| Function        | Description     |

|-----------------|-----------------|

| `doesNothing()` | Returns `Unit`. |



### Implicit stubbing of functions returning Unit



Mockative automatically stubs functions returning `Unit`, based on the idea that such functions are

typically used for verification rather than stubbing, and stubbing them could thus be considered

boilerplate, while they are trivially automatically stubbed.



You can opt out of this behaviour on the project level through your **build.gradle.kts** file:



**build.gradle.kts**



```kotlin

mockative {

    stubsUnitByDefault = false

}

```



Alternatively, you can opt out (or opt-in if you've opted out on the project level), using the

`configure(mock, block)` function either inline:



```kotlin

@Mock

val api = configure(mock(of())) { stubsUnitByDefault = false }

```



Or as needed:



```kotlin

@Mock

val api = mock(of())



@Test

fun test() {

    configure(api) { stubsUnitByDefault = false }

}

```



The configuration is stored on the mock instance. It must be configured before receiving any

invocations.



## Generic Types



When mocking a generic type use the ` of(): KClass` function to retain the type

arguments when passed to the ` mock(KClass)` function. You can use the `of` function

regardless of whether you're mocking a generic or non-generic type.



```kotlin

class GenericTypeTest {

    @Mock

    val list = mock(of>())

}

```



## Verification



Verification of invocations on mocks is supported through the `verify` and `coVerify` functions

using either values or matchers as per the stubbing (`every`) API:



### Verification using values



```kotlin

// Verify a `suspend` function (notice the use of `coVerify`)

coVerify { githubApi.getRepository("mockative/mockative") }

    .wasNotInvoked()



// Verify a blocking function

verify { repositoryMapper.mapResponseToRepository(response) }

    .wasInvoked(atLeast = 1)



// Verify a property getter

verify { repository.maintainer }

    .wasInvoked(atLeast = once, atMost = 6)



// Verify a property setter

verify { repository.stars = repository.stars + 1 }

    .wasInvoked(exactly = 1)

```



### Verification using matchers



```kotlin

// Verify a suspend function (notice the use of `coVerify`)

coVerify { s3Client.getObject(eq(request), any()) }

    .wasInvoked(exactly = once)

```



## Validation



In addition to verification of expectations there's also validation of the use of expectations,

which, if not used, can lead to both "under verification" and "over mocking" resulting in

inaccurate tests. To handle such cases Mockative provides 2 functions you can use on your mocks,

usually in the `@AfterTest` function of your tests:



```kotlin

@AfterTest

fun afterTest() {

    // Verifies that all expectations were verified through a call to `verify { ... }.wasInvoked()`.

    verifyNoUnverifiedExpectations(githubApi)



    // Verifies that the mock has no expectations that weren't invoked at least once.

    verifyNoUnmetExpectations(s3Client)

}

```