[Test] Add TestFormulaObserver.input() (#209)

* [Test] Add TestFormulaObserver.input()

* Ensure formula is running.

* Assert no errors before interaction as well.

Author: Laimiux

CHANGELOG.md

@@ -35,6 +35,8 @@
 - Move `FragmentContract` into `android` package.
 - Move `FragmentFlowState` into `android` package.
 - Move `FragmentFlowStore` into `android` package.
+- **Breaking**: Replaced `formula.test(inputObservable)` with `formula.test().input()` 
+- Add `TestFormulaObserver.assertNoErrors()`
 
 ## [0.6.1] - November 18, 2020
 - Bugfix: Fix runtime ignoring `Formula.key` for the root formula.

formula-test/src/main/java/com/instacart/formula/test/TestFormulaObserver.kt

@@ -2,34 +2,59 @@ package com.instacart.formula.test
 
 import com.instacart.formula.IFormula
 import com.instacart.formula.rxjava3.toObservable
-import io.reactivex.rxjava3.core.Observable
+import io.reactivex.rxjava3.subjects.BehaviorSubject
 
 class TestFormulaObserver<Input : Any, Output : Any, FormulaT : IFormula<Input, Output>>(
-    private val input: Observable<Input>,
     val formula: FormulaT
 ) {
 
+    private var started: Boolean = false
+    private val inputRelay = BehaviorSubject.create<Input>()
     private val observer = formula
-        .toObservable(input)
+        .toObservable(inputRelay)
         .test()
         .assertNoErrors()
 
     fun values(): List<Output> {
         return observer.values()
     }
 
+    /**
+     * Passes input to [formula].
+     */
+    fun input(value: Input) = apply {
+        started = true
+        assertNoErrors() // Check before interaction
+        inputRelay.onNext(value)
+        assertNoErrors() // Check after interaction
+    }
+
     inline fun output(assert: Output.() -> Unit) = apply {
+        ensureFormulaIsRunning()
+        assertNoErrors() // Check before interaction
         assert(values().last())
+        assertNoErrors() // Check after interaction
     }
 
     fun assertOutputCount(count: Int) = apply {
+        ensureFormulaIsRunning()
+        assertNoErrors()
         val size = values().size
         assert(size == count) {
             "Expected: $count, was: $size"
         }
     }
 
+    fun assertNoErrors() = apply {
+        observer.assertNoErrors()
+    }
+
     fun dispose() = apply {
         observer.dispose()
     }
+
+    @PublishedApi
+    internal fun ensureFormulaIsRunning() {
+        if (!started) throw IllegalStateException("Formula is not running. Call [TeatFormulaObserver.input] to start it.")
+    }
 }

formula-test/src/main/java/com/instacart/formula/test/TestRuntimeExtensions.kt

@@ -2,37 +2,27 @@ package com.instacart.formula.test
 
 import com.instacart.formula.IFormula
 import com.instacart.formula.Stream
-import io.reactivex.rxjava3.core.Observable
 
 /**
  * An extension function to create a [TestFormulaObserver] for a [IFormula] instance.
  *
- * @param input Input passed to [IFormula].
+ * Note: Formula won't start until you pass it an [input][TestFormulaObserver.input].
  */
-fun <Input : Any, Output : Any, F: IFormula<Input, Output>> F.test(
-    input: Input
-): TestFormulaObserver<Input, Output, F> {
-    return test(Observable.just(input))
+fun <Input : Any, Output : Any, F: IFormula<Input, Output>> F.test(): TestFormulaObserver<Input, Output, F> {
+    return TestFormulaObserver(this)
 }
 
-
 /**
  * An extension function to create a [TestFormulaObserver] for a [IFormula] instance.
  *
- * @param input A stream of inputs passed to [IFormula].
+ * @param initialInput Input passed to [IFormula].
  */
 fun <Input : Any, Output : Any, F: IFormula<Input, Output>> F.test(
-    input: Observable<Input>
+    initialInput: Input
 ): TestFormulaObserver<Input, Output, F> {
-    return TestFormulaObserver(
-        input = input,
-        formula = this
-    )
+    return test().apply {
+        input(initialInput)
+    }
 }
 
-/**
- * An extension function to create a [TestFormulaObserver] for a [IFormula] instance.
- */
-fun <Output : Any, F: IFormula<Unit, Output>> F.test() = test(Unit)
-
 fun <Message> Stream<Message>.test() = TestStreamObserver(this)

formula-test/src/test/java/com/instacart/formula/test/TestFormulaTest.kt

@@ -16,7 +16,7 @@ class TestFormulaTest {
     @Before fun setup() {
         childFormula = FakeChildFormula()
         parentFormula = ParentFormula(childFormula)
-        subject = ParentFormula(childFormula = childFormula).test()
+        subject = ParentFormula(childFormula = childFormula).test(Unit)
     }
 
     @Test fun `trigger callback using child input`() {

formula/src/test/java/com/instacart/formula/ChildRemovedOnMessage.kt

@@ -13,7 +13,7 @@ class ChildRemovedOnMessage {
                 }
             )
         })
-        .test()
+        .test(Unit)
 
     fun assertChildIsVisible(visible: Boolean) = apply {
         subject.output {

formula/src/test/java/com/instacart/formula/ChildStreamEvents.kt

@@ -6,7 +6,7 @@ import com.instacart.formula.test.test
 class ChildStreamEvents {
 
     private val child = StartStopFormula()
-    private val subject = HasChildFormula(child).test()
+    private val subject = HasChildFormula(child).test(Unit)
 
     fun startListening() = apply {
         subject.output { child.startListening() }

formula/src/test/java/com/instacart/formula/DuplicateChildrenTest.kt

@@ -9,7 +9,7 @@ import kotlin.IllegalStateException
 class DuplicateChildrenTest {
 
     @Test fun `adding duplicate child throws an exception`() {
-        val error = Try { ParentFormula().test() }.errorOrNull()?.cause
+        val error = Try { ParentFormula().test(Unit) }.errorOrNull()?.cause
         assertThat(error).isInstanceOf(IllegalStateException::class.java)
     }
 

formula/src/test/java/com/instacart/formula/DynamicFormulaInputTest.kt

@@ -2,15 +2,17 @@ package com.instacart.formula
 
 import com.google.common.truth.Truth.assertThat
 import com.instacart.formula.test.test
-import io.reactivex.rxjava3.core.Observable
 import org.junit.Test
 
 class DynamicFormulaInputTest {
 
     @Test
     fun `using dynamic input`() {
         TestFormula()
-            .test(Observable.just(1, 2, 3))
+            .test()
+            .input(1)
+            .input(2)
+            .input(3)
             .apply {
                 assertThat(values()).containsExactly(1, 2, 3).inOrder()
             }

formula/src/test/java/com/instacart/formula/DynamicStreamSubject.kt

@@ -2,14 +2,12 @@ package com.instacart.formula
 
 import com.google.common.truth.Truth.assertThat
 import com.instacart.formula.test.test
-import com.jakewharton.rxrelay3.PublishRelay
 
 class DynamicStreamSubject {
-    private val streams = PublishRelay.create<List<String>>()
-    private val subject = TestFormula().test(streams)
+    private val subject = TestFormula().test()
 
     fun updateStreams(vararg keys: String) = apply {
-        streams.accept(keys.asList())
+        subject.input(keys.asList())
         assertRunning(*keys)
     }
 

formula/src/test/java/com/instacart/formula/FetchDataExampleTest.kt

@@ -11,7 +11,7 @@ class FetchDataExampleTest {
     @Test fun `fake network example`() {
 
         MyFormula()
-            .test()
+            .test(Unit)
             .apply {
                 values().last().onChangeId("1")
                 values().last().onChangeId("2")