Hookup MvRxMocker and add tests

mvrx/src/main/kotlin/com/airbnb/mvrx/BaseMvRxViewModel.kt

@@ -10,6 +10,7 @@ import io.reactivex.Single
 import io.reactivex.android.schedulers.AndroidSchedulers
 import io.reactivex.disposables.CompositeDisposable
 import io.reactivex.disposables.Disposable
+import io.reactivex.disposables.Disposables
 import io.reactivex.functions.Consumer
 import io.reactivex.schedulers.Schedulers
 import kotlin.reflect.KProperty1
@@ -24,10 +25,12 @@ abstract class BaseMvRxViewModel<S : MvRxState>(
     initialState: S,
     private val debugMode: Boolean = false
 ) : ViewModel() {
+
+    internal val stateStore: MvRxStateStore<S> = MvRxStateStore(initialState)
+
     private val tag by lazy { javaClass.simpleName }
     private val disposables = CompositeDisposable()
     private val backgroundScheduler = Schedulers.single()
-    private val stateStore: MvRxStateStore<S> = MvRxStateStore(initialState)
 
     init {
         if (debugMode) {
@@ -57,17 +60,16 @@ abstract class BaseMvRxViewModel<S : MvRxState>(
      *    mutable variables or properties from outside the lambda or else it may crash.
      */
     protected fun setState(reducer: S.() -> S) {
-        if (debugMode) {
-            // Must use `set` to ensure the validated state is the same as the actual state used in reducer
-            // Do not use `get` since `getState` queue has lower priority and the validated state would be the state after reduced
-            stateStore.set {
-                val firstState = this.reducer()
-                val secondState = this.reducer()
-                if (firstState != secondState) throw IllegalArgumentException("Your reducer must be pure!")
-                firstState
-            }
-        } else {
-            stateStore.set(reducer)
+        when {
+            debugMode -> // Must use `set` to ensure the validated state is the same as the actual state used in reducer
+                // Do not use `get` since `getState` queue has lower priority and the validated state would be the state after reduced
+                stateStore.set {
+                    val firstState = this.reducer()
+                    val secondState = this.reducer()
+                    if (firstState != secondState) throw IllegalArgumentException("Your reducer must be pure!")
+                    firstState
+                }
+            else -> stateStore.set(reducer)
         }
     }
 
@@ -137,6 +139,10 @@ abstract class BaseMvRxViewModel<S : MvRxState>(
         successMetaData: ((T) -> Any)? = null,
         stateReducer: S.(Async<V>) -> S
     ): Disposable {
+        if (stateStore.isMocked) {
+            return Disposables.disposed()
+        }
+
         // This will ensure that Loading is dispatched immediately rather than being posted to `backgroundScheduler` before emitting Loading.
         setState { stateReducer(Loading()) }
 

mvrx/src/main/kotlin/com/airbnb/mvrx/MvRxStateStore.kt

@@ -5,7 +5,7 @@ import io.reactivex.disposables.CompositeDisposable
 import io.reactivex.disposables.Disposable
 import io.reactivex.schedulers.Schedulers
 import io.reactivex.subjects.BehaviorSubject
-import java.util.LinkedList
+import java.util.*
 
 /**
  * This is a container class around the actual state itself. It has a few optimizations to ensure
@@ -15,7 +15,11 @@ import java.util.LinkedList
  * conditions with each other.
  *
  */
-internal open class MvRxStateStore<S : Any>(initialState: S) : Disposable {
+internal open class MvRxStateStore<S : Any>(
+    initialState: S
+) : Disposable {
+
+    internal val isMocked = MvRxMocker.enabled
     /**
      * The subject is where state changes should be pushed to.
      */
@@ -39,8 +43,8 @@ internal open class MvRxStateStore<S : Any>(initialState: S) : Disposable {
      * current state.
      */
     val state: S
-        // value must be present here, since the subject is created with initialState
-        get() = subject.value!!
+    // value must be present here, since the subject is created with initialState
+        get() = MvRxMocker.getMockedState(this) ?: subject.value!!
 
     init {
 
@@ -57,8 +61,10 @@ internal open class MvRxStateStore<S : Any>(initialState: S) : Disposable {
      * are guaranteed to run before the get block is run.
      */
     fun get(block: (S) -> Unit) {
-        jobs.enqueueGetStateBlock(block)
-        flushQueueSubject.onNext(Unit)
+        MvRxMocker.getMockedState(this)?.let(block) ?: run {
+            jobs.enqueueGetStateBlock(block)
+            flushQueueSubject.onNext(Unit)
+        }
     }
 
     /**
@@ -72,6 +78,8 @@ internal open class MvRxStateStore<S : Any>(initialState: S) : Disposable {
      * all of the code required.
      */
     fun set(stateReducer: S.() -> S) {
+        if (MvRxMocker.getMockedState(this) != null) return
+
         jobs.enqueueSetStateBlock(stateReducer)
         flushQueueSubject.onNext(Unit)
     }
@@ -131,8 +139,8 @@ internal open class MvRxStateStore<S : Any>(initialState: S) : Disposable {
         val blocks = jobs.dequeueAllSetStateBlocks() ?: return
 
         blocks
-                .fold(state) { state, reducer -> state.reducer() }
-                .run { subject.onNext(this) }
+            .fold(state) { state, reducer -> state.reducer() }
+            .run { subject.onNext(this) }
     }
 
     private fun handleError(throwable: Throwable) {

mvrx/src/main/kotlin/com/airbnb/mvrx/TestUtil.kt

@@ -0,0 +1,38 @@
+package com.airbnb.mvrx
+
+
+/**
+ * This singleton can be used to provide mocked states to viewModels for testing.
+ * State can be directly set or set via arguments. Set the mocker to enabled
+ * to have the viewModels use these mocked states.
+ */
+object MvRxMocker {
+
+    /**
+     * Enable or disable whether the viewModels use mocked states
+     */
+    var enabled: Boolean = false
+    private val mockedState: MutableMap<MvRxStateStore<*>, MvRxState?> = mutableMapOf()
+
+    /**
+     * Set a mock state on a viewModel directly
+     */
+    fun <S : MvRxState> setMockedState(viewModel: BaseMvRxViewModel<S>, state: S?) {
+        mockedState[viewModel.stateStore] = state
+    }
+
+    /**
+     * Set a mock state on a viewModel via arguments
+     */
+    fun <S : MvRxState> setMockedStateFromArgs(viewModel: BaseMvRxViewModel<S>, args: Any?) {
+        setMockedState(viewModel, _initialStateProvider(viewModel.state::class.java, args))
+    }
+
+    /**
+     * Return the mocked state for a viewModel if one has been set, otherwise return null
+     */
+    internal fun <S : Any> getMockedState(stateStore: MvRxStateStore<S>): S? {
+        @Suppress("UNCHECKED_CAST")
+        return if (enabled) mockedState[stateStore] as? S else null
+    }
+}

mvrx/src/test/kotlin/com/airbnb/mvrx/MvRxMockerTest.kt

@@ -0,0 +1,60 @@
+package com.airbnb.mvrx
+
+import junit.framework.Assert
+import org.junit.Test
+
+class MvRxMockerTest : BaseTest() {
+
+    private val initialState = TestState("initial", 0)
+    private val mockState = TestState("updated", 1)
+
+    @Test
+    fun testDisabled() {
+        MvRxMocker.enabled = false
+
+        val viewModel = TestViewModel(initialState)
+        MvRxMocker.setMockedState(viewModel, mockState)
+
+        withState(viewModel) { state ->
+            Assert.assertEquals(state, initialState)
+        }
+    }
+
+    @Test
+    fun testEnabled() {
+        MvRxMocker.enabled = true
+
+        val viewModel = TestViewModel(initialState)
+        MvRxMocker.setMockedState(viewModel, mockState)
+
+        withState(viewModel) { state ->
+            Assert.assertEquals(mockState, state)
+        }
+    }
+
+    @Test
+    fun testMockNotSet() {
+        MvRxMocker.enabled = true
+
+        val viewModel = TestViewModel(initialState)
+
+        withState(viewModel) { state ->
+            Assert.assertEquals(initialState, state)
+        }
+    }
+
+    @Test
+    fun testMockArgs() {
+        MvRxMocker.enabled = true
+
+        val viewModel = TestViewModel(initialState)
+        val args = ParcelableArgs("test args")
+        MvRxMocker.setMockedStateFromArgs(viewModel, args)
+
+        withState(viewModel) { state ->
+            Assert.assertEquals(TestState(args), state)
+        }
+    }
+
+    private class TestViewModel(initialState: TestState) : TestMvRxViewModel<TestState>(initialState)
+}