Refactor coroutine testing setup (#1583)

* coroutine-utils: init

* coroutine-utils-testing: init

* format-common: switch over to using DispatcherProvider

* Convert Binds method to an extension function

* Add Dispatcher module

coroutine-utils-testing/api/coroutine-utils-testing.api

@@ -0,0 +1,8 @@
+public final class dev/msfjarvis/aps/test/CoroutineTestRule : org/junit/rules/TestWatcher {
+	public fun <init> ()V
+	public fun <init> (Lkotlinx/coroutines/test/TestDispatcher;)V
+	public synthetic fun <init> (Lkotlinx/coroutines/test/TestDispatcher;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public final fun getTestDispatcher ()Lkotlinx/coroutines/test/TestDispatcher;
+	public final fun getTestDispatcherProvider ()Ldev/msfjarvis/aps/util/coroutines/DispatcherProvider;
+}
+

coroutine-utils-testing/build.gradle.kts

@@ -0,0 +1,14 @@
+/*
+ * Copyright © 2014-2021 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+plugins {
+  kotlin("jvm")
+  id("com.github.android-password-store.kotlin-library")
+}
+
+dependencies {
+  implementation(projects.coroutineUtils)
+  implementation(libs.testing.junit)
+  implementation(libs.kotlin.coroutines.test)
+}

coroutine-utils-testing/src/main/kotlin/dev/msfjarvis/aps/test/CoroutineTestRule.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright © 2014-2021 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package dev.msfjarvis.aps.test
+
+import dev.msfjarvis.aps.util.coroutines.DispatcherProvider
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.TestCoroutineScheduler
+import kotlinx.coroutines.test.TestDispatcher
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.setMain
+import org.junit.rules.TestWatcher
+import org.junit.runner.Description
+
+/**
+ * JUnit [TestWatcher] to correctly handle setting and resetting a given [testDispatcher] for tests.
+ */
+@ExperimentalCoroutinesApi
+public class CoroutineTestRule(
+  public val testDispatcher: TestDispatcher = UnconfinedTestDispatcher(TestCoroutineScheduler()),
+) : TestWatcher() {
+
+  public val testDispatcherProvider: DispatcherProvider =
+    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()
+  }
+}