In order to store state in jetpack compose I have so far used the the following pattern:
private val _largeDataClass:MutableState<LargeDataClass> = mutableStateOf(LargeDataClass())
val largeDataClass :State<LargeDataClass> = _largeDataClass
then I display some or all of the properties of this class in my composition. When the user changes a property of this data class I need to update the state and I do it in the following way:
fun onUserEvent(somePropertyChange:String){
_largeDataClass.value=largeDataClass.value.copy(someProperty = somePropertyChange)
}
I got this approach from the following post. It works and has the benefit of keeping my codebase relatively small (as there might be 20+ different properties in LargeDataClass that I dont need to declare individually as mutable state) BUT, if I am not mistaken, following this approach will trigger the recomposition of my entire screen even if the user just types a single letter in one of my many TextFields. As all my composables display some property of largeDataClass and they have just been notified that its value has changed.
My first question is wether I am right in this last assumption. Will my current way of holding state negatively affect my apps performance because I am forcing the screen to redraw itself completely constantly? Or are there some optimizations, that I'm unaware of, in compose that prevent this from happening and render my appoach safe?
my second question: I would really love it if there was a way of turning a data class, say:
data class Student(
val key: String = "s0",
val firstName: String = "",
val lastName: String = "")
into an equivalent state holder class (something similar to the following)
class StudentState(s:Student){
val key= mutableStateOf(s:Key),
val firstName= mutableStateOf(s.firstName),
val lastName= mutableStateOf(s.lastName)}
(Ideally without having to explicitly write such a class myself every time) Does this exist already? is there a way of using reflection or the like to achieve this for a generic data class?
I am still learning to deal with state in jetpack compose and I want to get it right. It seems to me that tracking the properties of my data classes individually either in the ViewModel or in a State Holder class is the right thing to do, but on the other hand this makes my code a lot longer and it just feels like I am doing a lot of stuff twice and my code becomes less readable and maintainable. Any insights are much appreciated
You could use reflection to create mutableStates for the members of any class like so:
fun createStateMap(baseObject: Any) = with(baseObject::class.memberProperties) {
map { it.name }.zip(map { mutableStateOf(it.getter.call(baseObject)) }).toMap()
}
And then use it like this:
class MyViewModel : ViewModel() {
private val student = Student(firstName = "John", lastName = "Doe")
val studentStateMap = createStateMap(student)
}
#Composable
fun MyComposable(viewModel: MyViewModel) {
val student = viewModel.studentStateMap
Button(
onClick = { student["firstName"]?.value = "Jack" }
) {
Text(text = student["firstName"]?.value.toString())
}
}
I wouldn't use it, it's not typesafe, it's messy and ugly, but it's possible.
An Annotation to store data class #AsState
Well I am still not sure about wether it is fine to simply .copy(changedValue = "...") a large data class or if this is inefficient because it triggers unecessary recompositions.
In any case just to be safe (and cause I think its cleaner) I wrote an AnnotationProcessor that takes my data classes and creates both a mutable and immutable version of the class holding all properties as state. It supports both lists and maps but is shallow (meaning that it wont repeat the same process for nested classes). Here an example of the class with the annotation and the result.
please let me know if you consider this to be usefull in order to track state more cleanly when a data class is displayed/edited in a composable (and also if you dont)
The original class
#AsState
data class Test(val name:String, val age:Int, val map:HashMap<String,Int>, val list:ArrayList<String>)
The mutable verion of the class with a custonm constructor and rootClass getter
public class TestMutableState {
public val name: MutableState<String>
public val age: MutableState<Int>
public val map: SnapshotStateMap<String, Int>
public val list: SnapshotStateList<String>
public constructor(rootObject: Test) {
this.name=mutableStateOf(rootObject.name)
this.age=mutableStateOf(rootObject.age)
this.map=rootObject.map.map{Pair(it.key,it.value)}.toMutableStateMap()
this.list=rootObject.list.toMutableStateList()
}
public fun getTest(): Test = Test(name = this.name.value,
age = this.age.value,
map = HashMap(this.map),
list = ArrayList(this.list),
)
}
The immutable version that can be public in the ViewModel
public class TestState {
public val name: State<String>
public val age: State<Int>
public val map: SnapshotStateMap<String, Int>
public val list: SnapshotStateList<String>
public constructor(mutableObject: TestMutableState) {
this.name=mutableObject.name
this.age=mutableObject.age
this.map=mutableObject.map
this.list=mutableObject.list
}
}
TL;DR
Next I am pasting the source code for my annotation processor so you can implement it. I basically followed this article and implemented some of my own changes based on arduous googling. I might make this a module in the future so that other people can more easily implement this in their projects i there is any interest:
Annotation class
#Target(AnnotationTarget.CLASS)
#Retention(AnnotationRetention.SOURCE)
public annotation class AsState
Annotation processor
#AutoService(Processor::class)
class AnnotationProcessor : AbstractProcessor() {
companion object {
const val KAPT_KOTLIN_GENERATED_OPTION_NAME = "kapt.kotlin.generated"
}
override fun getSupportedAnnotationTypes(): MutableSet<String> {
return mutableSetOf(AsState::class.java.name)
}
override fun getSupportedSourceVersion(): SourceVersion = SourceVersion.latest()
override fun process(annotations: MutableSet<out TypeElement>?, roundEnv: RoundEnvironment): Boolean {
roundEnv.getElementsAnnotatedWith(AsState::class.java)
.forEach {
if (it.kind != ElementKind.CLASS) {
processingEnv.messager.printMessage(Diagnostic.Kind.ERROR, "Only classes can be annotated")
return true
}
processAnnotation(it)
}
return false
}
#OptIn(KotlinPoetMetadataPreview::class, com.squareup.kotlinpoet.DelicateKotlinPoetApi::class)
private fun processAnnotation(element: Element) {
val className = element.simpleName.toString()
val pack = processingEnv.elementUtils.getPackageOf(element).toString()
val kmClass = (element as TypeElement).toImmutableKmClass()
//create vessel for mutable state class
val mutableFileName = "${className}MutableState"
val mutableFileBuilder= FileSpec.builder(pack, mutableFileName)
val mutableClassBuilder = TypeSpec.classBuilder(mutableFileName)
val mutableConstructorBuilder= FunSpec.constructorBuilder()
.addParameter("rootObject",element.asType().asTypeName())
var helper="return ${element.simpleName}("
//create vessel for immutable state class
val stateFileName = "${className}State"
val stateFileBuilder= FileSpec.builder(pack, stateFileName)
val stateClassBuilder = TypeSpec.classBuilder(stateFileName)
val stateConstructorBuilder= FunSpec.constructorBuilder()
.addParameter("mutableObject",ClassName(pack,mutableFileName))
//import state related libraries
val mutableStateClass= ClassName("androidx.compose.runtime","MutableState")
val stateClass=ClassName("androidx.compose.runtime","State")
val snapshotStateMap= ClassName("androidx.compose.runtime.snapshots","SnapshotStateMap")
val snapshotStateList=ClassName("androidx.compose.runtime.snapshots","SnapshotStateList")
fun processMapParameter(property: ImmutableKmValueParameter) {
val clName =
((property.type?.abbreviatedType?.classifier) as KmClassifier.TypeAlias).name
val arguments = property.type?.abbreviatedType?.arguments?.map {
ClassInspectorUtil.createClassName(
((it.type?.classifier) as KmClassifier.Class).name
)
}
val paramClass = ClassInspectorUtil.createClassName(clName)
val elementPackage = clName.replace("/", ".")
val paramName = property.name
arguments?.let {
mutableClassBuilder.addProperty(
PropertySpec.builder(
paramName,
snapshotStateMap.parameterizedBy(it), KModifier.PUBLIC
)
.build()
)
}
arguments?.let {
stateClassBuilder.addProperty(
PropertySpec.builder(
paramName,
snapshotStateMap.parameterizedBy(it), KModifier.PUBLIC
)
.build()
)
}
helper = helper.plus("${paramName} = ${paramClass.simpleName}(this.${paramName}),\n")
mutableConstructorBuilder
.addStatement("this.${paramName}=rootObject.${paramName}.map{Pair(it.key,it.value)}.toMutableStateMap()")
stateConstructorBuilder
.addStatement("this.${paramName}=mutableObject.${paramName}")
}
fun processListParameter(property: ImmutableKmValueParameter) {
val clName =
((property.type?.abbreviatedType?.classifier) as KmClassifier.TypeAlias).name
val arguments = property.type?.abbreviatedType?.arguments?.map {
ClassInspectorUtil.createClassName(
((it.type?.classifier) as KmClassifier.Class).name
)
}
val paramClass = ClassInspectorUtil.createClassName(clName)
val elementPackage = clName.replace("/", ".")
val paramName = property.name
arguments?.let {
mutableClassBuilder.addProperty(
PropertySpec.builder(
paramName,
snapshotStateList.parameterizedBy(it), KModifier.PUBLIC
)
.build()
)
}
arguments?.let {
stateClassBuilder.addProperty(
PropertySpec.builder(
paramName,
snapshotStateList.parameterizedBy(it), KModifier.PUBLIC
)
.build()
)
}
helper = helper.plus("${paramName} = ${paramClass.simpleName}(this.${paramName}),\n")
mutableConstructorBuilder
.addStatement("this.${paramName}=rootObject.${paramName}.toMutableStateList()")
stateConstructorBuilder
.addStatement("this.${paramName}=mutableObject.${paramName}")
}
fun processDefaultParameter(property: ImmutableKmValueParameter) {
val clName = ((property.type?.classifier) as KmClassifier.Class).name
val paramClass = ClassInspectorUtil.createClassName(clName)
val elementPackage = clName.replace("/", ".")
val paramName = property.name
mutableClassBuilder.addProperty(
PropertySpec.builder(
paramName,
mutableStateClass.parameterizedBy(paramClass), KModifier.PUBLIC
).build()
)
stateClassBuilder.addProperty(
PropertySpec.builder(
paramName,
stateClass.parameterizedBy(paramClass),
KModifier.PUBLIC
).build()
)
helper = helper.plus("${paramName} = this.${paramName}.value,\n")
mutableConstructorBuilder
.addStatement(
"this.${paramName}=mutableStateOf(rootObject.${paramName}) "
)
stateConstructorBuilder
.addStatement("this.${paramName}=mutableObject.${paramName}")
}
for (property in kmClass.constructors[0].valueParameters) {
val javaPackage = (property.type!!.classifier as KmClassifier.Class).name.replace("/", ".")
val javaClass=try {
Class.forName(javaPackage)
}catch (e:Exception){
String::class.java
}
when{
Map::class.java.isAssignableFrom(javaClass) ->{ //if property is of type map
processMapParameter(property)
}
List::class.java.isAssignableFrom(javaClass) ->{ //if property is of type list
processListParameter(property)
}
else ->{ //all others
processDefaultParameter(property)
}
}
}
helper=helper.plus(")") //close off method
val getRootBuilder= FunSpec.builder("get$className")
.returns(element.asClassName())
getRootBuilder.addStatement(helper.toString())
mutableClassBuilder.addFunction(mutableConstructorBuilder.build()).addFunction(getRootBuilder.build())
stateClassBuilder.addFunction(stateConstructorBuilder.build())
val kaptKotlinGeneratedDir = processingEnv.options[KAPT_KOTLIN_GENERATED_OPTION_NAME]
val mutableFile = mutableFileBuilder
.addImport("androidx.compose.runtime", "mutableStateOf")
.addImport("androidx.compose.runtime","toMutableStateMap")
.addImport("androidx.compose.runtime","toMutableStateList")
.addType(mutableClassBuilder.build())
.build()
mutableFile.writeTo(File(kaptKotlinGeneratedDir))
val stateFile = stateFileBuilder
.addType(stateClassBuilder.build())
.build()
stateFile.writeTo(File(kaptKotlinGeneratedDir))
}
}
gradle annotation
plugins {
id 'java-library'
id 'org.jetbrains.kotlin.jvm'
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
}
java {
sourceCompatibility = JavaVersion.VERSION_1_8
targetCompatibility = JavaVersion.VERSION_1_8
}
gradle processor
plugins {
id 'kotlin'
id 'kotlin-kapt'
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation project(':annotations')
implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.6.10"
// https://mvnrepository.com/artifact/com.squareup/kotlinpoet
implementation 'com.squareup:kotlinpoet:1.10.2'
implementation "com.squareup:kotlinpoet-metadata:1.7.1"
implementation "com.squareup:kotlinpoet-metadata-specs:1.7.1"
implementation "com.google.auto.service:auto-service:1.0.1"
// https://mvnrepository.com/artifact/org.jetbrains.kotlinx/kotlinx-metadata-jvm
implementation "org.jetbrains.kotlinx:kotlinx-metadata-jvm:0.4.2"
implementation 'org.json:json:20211205'
kapt "com.google.auto.service:auto-service:1.0.1"
}
java {
sourceCompatibility = JavaVersion.VERSION_1_8
targetCompatibility = JavaVersion.VERSION_1_8
}
Related
I am trying to test a repository ExpensesRepository
class ExpensesRepository #Inject constructor(
private val store: DataStore
) : AbstractRepository<Expense> {
override fun get(offset: Int, limit: Int): List<Expense?> =
store.getAll(offset, limit)
override fun get(key: String): Expense? = store.getOne(key = key)
override fun create(input: Expense) =
store.create(key = input.key, element = input)
override fun delete(key: String) = store.remove(key = key)
override fun update(
key: String,
update: Expense
): Expense =
store.update(key = key, element = update)
override fun removeAll() = store.flush()
}
In the test suite I have mocked the store parameter using mockito, then I stubbed that mock's method getOne(String) to return an expense object from my fixtures.
Here is my test suite
class ExpensesRepositoryTest {
#get:Rule
var instantTaskExecutorRule = InstantTaskExecutorRule()
private lateinit var repository: ExpensesRepository
private val dataStore = mock<DataStore>()
private val expense = Expense(
"key",
1,
"name",
"date",
12.12
)
private val expenseList = listOf(
expense,
expense,
expense
)
private val dummyKey = "expense_key"
#Before
fun setup() {
repository = ExpensesRepository(dataStore)
}
#Test
fun `should get an item with existing key`() {
whenever(dataStore.getOne<Expense>(dummyKey)).thenReturn(expense)
val result = repository.get(dummyKey)
verify(dataStore, Times(1)).getOne<Expense>(dummyKey)
assertThat(result).isEqualTo(expense)
}
}
When I run the test it fails cuz of NullPointerException and that's when the DataStore calls the function getOne(String) that I supposedly stubbed earlier. In case it helps here is the DataStore class
class DataStore(val store: Persistence, val gson: Gson) {
inline fun <reified R : Persistable> getAll(
offset: Int,
limit: Int
): List<R?> =
store.get(offset, limit).map { it.maybeMapTo<R>(mapper = gson) }
inline fun <reified R : Persistable> getOne(key: String): R? =
store.get(key).maybeMapTo<R>(mapper = gson)
fun create(key: String, element: Persistable) {
store.create(
key = key,
element = when (store) {
is JsonBased -> gson.toJson(element)
else -> element
}
)
}
inline fun <reified R : Persistable> update(
key: String,
element: R
): R {
return store.update(key, element) as R
}
fun remove(key: String) {
store.remove(key)
}
fun flush() {
store.flush()
}
}
Is there something I am doing wrong here?
I'm afraid you are out of luck: inline functions are not mockable.
would someone be able to show me how to make the getMovies function in this viewModel testable? I can't get the unit tests to await the coroutines properly..
(1) I'm pretty sure I have to create a test-CoroutineScope and a normal lifeCycle-CoroutineScope, as seen in this Medium Article.
(2) Once the scope definitions are made, I'm also unsure how to tell getMovies() which scope it should be using given a normal app context or a test context.
enum class MovieApiStatus { LOADING, ERROR, DONE }
class MovieListViewModel : ViewModel() {
var pageCount = 1
private val _status = MutableLiveData<MovieApiStatus>()
val status: LiveData<MovieApiStatus>
get() = _status
private val _movieList = MutableLiveData<List<Movie>>()
val movieList: LiveData<List<Movie>>
get() = _movieList
// allows easy update of the value of the MutableLiveData
private var viewModelJob = Job()
// the Coroutine runs using the Main (UI) dispatcher
private val coroutineScope = CoroutineScope(
viewModelJob + Dispatchers.Main
)
init {
Log.d("list", "in init")
getMovies(pageCount)
}
fun getMovies(pageNumber: Int) {
coroutineScope.launch {
val getMoviesDeferred =
MovieApi.retrofitService.getMoviesAsync(page = pageNumber)
try {
_status.value = MovieApiStatus.LOADING
val responseObject = getMoviesDeferred.await()
_status.value = MovieApiStatus.DONE
............
} catch (e: Exception) {
_status.value = MovieApiStatus.ERROR
................
}
}
pageCount = pageNumber.inc()
}
...
}
it uses this API service...
package com.example.themovieapp.network
import com.jakewharton.retrofit2.adapter.kotlin.coroutines.CoroutineCallAdapterFactory
import com.squareup.moshi.Moshi
import com.squareup.moshi.kotlin.reflect.KotlinJsonAdapterFactory
import kotlinx.coroutines.Deferred
import retrofit2.Retrofit
import retrofit2.converter.moshi.MoshiConverterFactory
import retrofit2.http.GET
import retrofit2.http.Query
private const val BASE_URL = "https://api.themoviedb.org/3/"
private const val API_key = ""
private val moshi = Moshi.Builder()
.add(KotlinJsonAdapterFactory())
.build()
private val retrofit = Retrofit.Builder()
.addConverterFactory(MoshiConverterFactory.create(moshi))
.addCallAdapterFactory(CoroutineCallAdapterFactory())
.baseUrl(BASE_URL)
.build()
interface MovieApiService{
//https://developers.themoviedb.org/3/movies/get-top-rated-movies
//https://square.github.io/retrofit/2.x/retrofit/index.html?retrofit2/http/Query.html
#GET("movie/top_rated")
fun getMoviesAsync(
#Query("api_key") apiKey: String = API_key,
#Query("language") language: String = "en-US",
#Query("page") page: Int
): Deferred<ResponseObject>
}
/*
Because this call is expensive, and the app only needs
one Retrofit service instance, you expose the service to the rest of the app using
a public object called MovieApi, and lazily initialize the Retrofit service there
*/
object MovieApi {
val retrofitService: MovieApiService by lazy {
retrofit.create(MovieApiService::class.java)
}
}
I'm simply trying to create a test which asserts the liveData 'status' is DONE after the function.
Here is the Project Repository
First you need to make your coroutine scope injectable somehow, either by creating a provider for it manually, or using an injection framework like dagger. That way, when you test your ViewModel, you can override the coroutine scope with a test version.
There are a few choices to do this, you can simply make the ViewModel itself injectable (article on that here: https://medium.com/chili-labs/android-viewmodel-injection-with-dagger-f0061d3402ff)
Or you can manually create a ViewModel provider and use that where ever it's created. No matter what, I would strongly advise some form of dependency injection in order to achieve real testability.
Regardless, your ViewModel needs to have its CoroutineScope provided, not instantiate the coroutine scope itself.
In other words you might want
class MovieListViewModel(val couroutineScope: YourCoroutineScope) : ViewModel() {}
or maybe
class MovieListViewModel #Inject constructor(val coroutineScope: YourCoroutineScope) : ViewModel() {}
No matter what you do for injection, the next step is to create your own CoroutineScope interface that you can override in the test context. For example:
interface YourCoroutineScope : CoroutineScope {
fun launch(block: suspend CoroutineScope.() -> Unit): Job
}
That way when you use the scope for your app, you can use one scope, say, lifecycle coroutine scope:
class LifecycleManagedCoroutineScope(
private val lifecycleCoroutineScope: LifecycleCoroutineScope,
override val coroutineContext: CoroutineContext = lifecycleCoroutineScope.coroutineContext) : YourCoroutineScope {
override fun launch(block: suspend CoroutineScope.() -> Unit): Job = lifecycleCoroutineScope.launchWhenStarted(block)
}
And for your test, you can use a test scope:
class TestScope(override val coroutineContext: CoroutineContext) : YourCoroutineScope {
val scope = TestCoroutineScope(coroutineContext)
override fun launch(block: suspend CoroutineScope.() -> Unit): Job {
return scope.launch {
block.invoke(this)
}
}
}
Now, since your ViewModel is using a scope of type YourCoroutineScope, and since, in the examples above, both the lifecycle and test version implement the YourCoroutineScope interface, you can use different versions of the scope in different situations, i.e. app vs test.
Ok, thanks to Dapp's answer, I was able to write some tests which seem to be awaiting the function Properly.
Here is a copy of what I did :)
enum class MovieApiStatus { LOADING, ERROR, DONE }
class MovieListViewModel(val coroutineScope: ManagedCoroutineScope) : ViewModel() {
//....creating vars, livedata etc.
init {
getMovies(pageCount)
}
fun getMovies(pageNumber: Int) =
coroutineScope.launch{
val getMoviesDeferred =
MovieApi.retrofitService.getMoviesAsync(page = pageNumber)
try {
_status.value = MovieApiStatus.LOADING
val responseObject = getMoviesDeferred.await()
_status.value = MovieApiStatus.DONE
if (_movieList.value == null) {
_movieList.value = ArrayList()
}
pageCount = pageNumber.inc()
_movieList.value = movieList.value!!.toList().plus(responseObject.results)
.sortedByDescending { it.vote_average }
} catch (e: Exception) {
_status.value = MovieApiStatus.ERROR
_movieList.value = ArrayList()
}
}
fun onLoadMoreMoviesClicked() =
getMovies(pageCount)
//...nav functions, clearing functions etc.
}
and here are the test cases
#ExperimentalCoroutinesApi
#RunWith(MockitoJUnitRunner::class)
class MovieListViewModelTest {
#get:Rule
var instantExecutorRule = InstantTaskExecutorRule()
private val testDispatcher = TestCoroutineDispatcher()
private val managedCoroutineScope: ManagedCoroutineScope = TestScope(testDispatcher)
lateinit var viewModel: MovieListViewModel
#Before
fun setup() {
//resProvider.mockColors()
Dispatchers.setMain(testDispatcher)
viewModel = MovieListViewModel(managedCoroutineScope)
}
#After
fun tearDown() {
Dispatchers.resetMain()
testDispatcher.cleanupTestCoroutines()
}
#ExperimentalCoroutinesApi
#Test
fun getMoviesTest() {
managedCoroutineScope.launch {
assertTrue(
"initial List, API status: ${viewModel.status.getOrAwaitValue()}",
viewModel.status.getOrAwaitValue() == MovieApiStatus.DONE
)
assertTrue(
"movieList has ${viewModel.movieList.value?.size}, != 20",
viewModel.movieList.value?.size == 20
)
assertTrue(
"pageCount = ${viewModel.pageCount}, != 2",
viewModel.pageCount == 2
)
viewModel.onLoadMoreMoviesClicked()
assertTrue(
"added to list, API status: ${viewModel.status.getOrAwaitValue()}",
viewModel.status.getOrAwaitValue() == MovieApiStatus.DONE
)
assertTrue(
"movieList has ${viewModel.movieList.value?.size}, != 40",
viewModel.movieList.value?.size == 40
)
}
}
}
It took some trial and error playing around with the Scopes.. runBlockingTest{} was causing an issue 'Exception: job() not completed'..
I also had to create a viewModel factory in order for the fragment to create the viewModel for when the app is running normally..
Project Repo
I have the following classes
interface CarsApi {
suspend fun fetchCar() : Car
}
class FetchCarUseCase(private val carsApi: CarsApi) {
suspend fun execute: Car = withContext(dispatcherProvider.io()) {
carsApi.fetchCar()
}
}
class ViewModel(private val fetchCarUseCase: FetchCarUseCase) {
private var car: Car
suspend fun retrieveCar() {
car = fetchCarUseCase.execute()
}
}
I want to write an ermetic test for the viewModel and the useCase:
#Test
fun testCarFetching() = runBlockingTest {
val aCar = Car()
val mockApi = mock<CarsApi>()
`when`(mockApi.fetchCar()).thenReturn(aCar)
val fetchCarUseCase = FetchCarUseCase(mockApi)
val viewModel = ViewModel(fetchCarUseCase)
viewModel.retrieveCar()
/* assert stuff on viewModel.car*/
}
But the viewModel.car always seems to be null. Inside the test body mockApi.fetchCar() does retrieve the provided value, but inside the FetchCarUseCase it does not. Also if I remove the suspend keyword from the interface, the mocking seems to be working fine.
At the moment, due to some other conditions I cannot use Mockk library, so I'm stuck with Mockito.
Am I missing something?
The used dependencies:
testImplementation 'junit:junit:4.12'
testImplementation 'org.mockito:mockito-core:2.28.2'
testImplementation('com.nhaarman.mockitokotlin2:mockito-kotlin:2.1.0') {
exclude module: 'mockito-core'
}
testImplementation 'org.jetbrains.kotlinx:kotlinx-coroutines-test:1.3.2
In case anyone else has to deal with this problem, here is the infrastructure I have build.
First, in all the classes that launch threads inject through the constructor or property a kotlinx.coroutines.DispatcherProvider. In my case it was just the useCase, but the viewModel might require it, as well.
class FetchCarUseCase(private val dispatcher: CoroutineDispatcher,
private val carsApi: CarsApi) {
suspend fun execute: Car = withContext(dispatcher) {
carsApi.fetchCar()
}
}
In the unit tests project, add a helper rule-class, in order to extract some functionality:
#ExperimentalCoroutinesApi
class CoroutineTestRule(val testDispatcher: TestCoroutineDispatcher = TestCoroutineDispatcher()) : TestWatcher() {
val testDispatcherProvider = object : DispatcherProvider {
override fun default(): CoroutineDispatcher = testDispatcher
override fun io(): CoroutineDispatcher = testDispatcher
override fun main(): CoroutineDispatcher = testDispatcher
override fun unconfined(): CoroutineDispatcher = testDispatcher
}
override fun starting(description: Description?) {
super.starting(description)
Dispatchers.setMain(testDispatcher)
}
override fun finished(description: Description?) {
super.finished(description)
Dispatchers.resetMain()
testDispatcher.cleanupTestCoroutines()
}
}
And finally the unit test looks like this:
#ExperimentalCoroutinesApi
#RunWith(MockitoJUnitRunner::class)
class ViewModelTest {
#get:Rule
var coroutinesTestRule = CoroutineTestRule()
#Test
fun testCarFetching() = coroutinesTestRule.testDispatcher.runBlockingTest {
val aCar = Car()
val mockApi = mock<CarsApi>()
`when`(mockApi.fetchCar()).thenReturn(aCar)
val fetchCarUseCase = FetchCarUseCase(mockApi)
val viewModel = ViewModel(fetchCarUseCase)
viewModel.retrieveCar()
/* assert stuff on viewModel.car*/
}
#Test
fun testCarFetchingError() = coroutinesTestRule.testDispatcher.runBlockingTest {
val aCar = Car()
val mockApi = mock<CarsApi>()
`when`(mockApi.fetchCar()).then {
throw Exception()
}
val fetchCarUseCase = FetchCarUseCase(mockApi)
val viewModel = ViewModel(fetchCarUseCase)
viewModel.retrieveCar()
/* assert stuff on erros*/
}
}
This way all the code in the unit tests runs on the same thread and in the same context.
I'm trying to learn unit testing, I have my code factored into an MVVM(i) architecture, but when I run my testParseToList() test function, it always comes back with an empty list and I can't figure out why. I fear it may have something to do with the i part of the MVVM(i) and whether or not I'm correctly mocking my viewmodel. I'm starting with my most simple viewmodel in hopes to get a grasp of the concepts before moving onto my more complex ones.
OfflineViewModelUnitTest.kt
#RunWith(JUnit4::class)
class OfflineViewModelUnitTest {
#get:Rule
val rule = InstantTaskExecutorRule()
#Mock
var offlineViewModel: OfflineViewModel = OfflineViewModel(OfflineInteractorImpl())
#Before
fun setup() {
MockitoAnnotations.initMocks(this)
DaggerOfflineViewModelComponent.builder()
.offlineInteractorImplModule(OfflineInteractorImplModule())
.build()
.inject(offlineViewModel)
// this.offlineViewModel = OfflineViewModel(OfflineInteractorImpl())
}
#Test
fun testParseToList() {
val test = offlineViewModel.parseTextToList("dried bonito extract,\n" +
" ketchup,\n" +
" millet,\n" +
" corn & wheat protein")
val a = "dried bonito extract"
val b = "ketchup"
val c = "millet"
val d = "corn & wheat protein"
val expectedResult = listOf(a, b, c, d)
assertEquals(expectedResult, test)
}
}
OfflineViewModel.kt
class OfflineViewModel(private val offlineInteractor: OfflineInteractor): ViewModel() {
init {
DaggerOfflineViewModelComponent.builder()
.offlineInteractorImplModule(OfflineInteractorImplModule())
.build()
.inject(this)
}
fun parseTextToList(firebaseVisionTextString: String): MutableList<String> {
Log.d("here it is", firebaseVisionTextString)
return offlineInteractor.parseTextToList(firebaseVisionTextString)
}
fun readCsvFromAssetFolder(inputStream: InputStream): List<String>{
return offlineInteractor.readCsvFromAssetFolder(inputStream)
}
}
OfflineInteractorImpl.kt
class OfflineInteractorImpl: OfflineInteractor {
override fun parseTextToList(firebaseVisionTextString: String): MutableList<String> {
val ingredientsList: MutableList<String> = firebaseVisionTextString.split(",").map { it.trim() }.toMutableList()
return ingredientsList
}
override fun readCsvFromAssetFolder(inputStream: InputStream): List<String> {
val csvLine: ArrayList<String> = ArrayList()
var content: Array<String>?
try
{
val br = BufferedReader(InputStreamReader(inputStream))
for (line in br.lines())
{
content = line.split((",").toRegex()).dropLastWhile{ it.isEmpty() }.toTypedArray()
csvLine.add(content[0].substringBefore(";"))
}
br.close()
}
catch (e: IOException) {
e.printStackTrace()
}
return csvLine
}
}
Test Results
java.lang.AssertionError:
Expected :[dried bonito extract, ketchup, millet, corn & wheat protein]
Actual :[]
Like second said, since you mocked offlineViewModel it is going to return an empty string, unless you define something for it to return using when().
Source: https://github.com/mockito/mockito/wiki/FAQ#what-values-do-mocks-return-by-default
I have the following class:
class LinkUserService() {
//** cake pattern **
oauthProvider: OAuthProvider =>
//******************
def isUserLinked(userId: String, service: String) = {
val cred = oauthProvider.loadCredential(userId)
cred != null
}
def linkUserAccount(userId: String, service: String): (String, Option[String]) = {
if (isUserLinked(userId, service)) {
("SERVICE_LINKED", None)
} else {
val authUrl = oauthProvider.newAuthorizationUrl
("SERVICE_NOT_LINKED", Some(authUrl))
}
}
def setLinkAuthToken(userId: String, service:String, token:String):String = {
oauthProvider.createAndStoreCredential(userId, token)
}
}
Typically I'd use this class in production like so:
val linkService = LinkUserService with GoogleOAuthProvider
When it comes to testing, I want to replace the oauthProvider with a mock such that's been trained by my unit test to respond like so: oauthProvider.loadCredential("nobody") returns null. Is this possible? If so, how would I set up my unit test to do so?
You have this problem because you are not using cake pattern to full extent. If you write something like
trait LinkUserServiceComponent {
this: OAuthProviderComponent =>
val linkUserService = new LinkUserService
class LinkUserService {
// use oauthProvider explicitly
...
}
}
trait GoogleOAuthProviderComponent {
val oauthProvider = new GoogleOAuthProvider
class GoogleOAuthProvider {
...
}
}
And then you use a mock like this:
val combinedComponent = new LinkUserServiceComponent with OAuthProviderComponent {
override val oauthProvider = mock(...)
}
Then your problem disappears. If you also make generic interface traits like this (and make other components depend on interface, not on implementation):
trait OAuthProviderComponent {
def oauthProvider: OAuthProvider
trait OAuthProvider {
// Interface declaration
}
}
then you also would have generic reusable and testable code.
This is very similar to your suggestion and it really is the essence of cake pattern.
The only solution I've been able to come up wiht is a sort of delegate mock trait as demonstrated:
trait MockOAuthProvider extends OAuthProvider {
val mockProvider = mock[OAuthProvider]
def loadCredential(userId: String) = mockProvider.loadCredential(userId)
def newAuthorizationUrl() = mockProvider.newAuthorizationUrl
def createAndStoreCredential(userId: String, authToken: String) = mockProvider.createAndStoreCredential(userId, authToken)
}
I place that at the top of my Spec, then when I declare my LinkUserService I mix in this Mock trait like so:
val linkUserService = new LinkUserService() with MockOAuthProvider
val mockOAuth = linkUserService.mockProvider
Finally in my unit tests I do things like:
mockOAuth.loadCredential("nobody") returns null
It works, but I could see that being a PITA if my trait was larger