Issue#67 Extract InstantExecutorExtension

test-util-junit5-android/src/main/AndroidManifest.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="org.fnives.test.showcase.android.testutil">
+
+</manifest>

test-util-junit5-android/src/main/java/org/fnives/test/showcase/android/testutil/InstantExecutorExtension.kt

@@ -0,0 +1,35 @@
+package org.fnives.test.showcase.android.testutil
+
+import android.annotation.SuppressLint
+import androidx.arch.core.executor.ArchTaskExecutor
+import androidx.arch.core.executor.TaskExecutor
+import org.junit.jupiter.api.extension.AfterEachCallback
+import org.junit.jupiter.api.extension.BeforeEachCallback
+import org.junit.jupiter.api.extension.ExtensionContext
+
+/**
+ * Junit5 Version of InstantTaskExecutorRule from Junit4
+ *
+ * reference: https://developer.android.com/reference/androidx/arch/core/executor/testing/InstantTaskExecutorRule
+ *
+ * A JUnit5 Extensions that swaps the background executor used by the Architecture Components with a different one which executes each task synchronously.
+ * You can use this extension for your host side tests that use Architecture Components.
+ */
+@SuppressLint("RestrictedApi")
+class InstantExecutorExtension : BeforeEachCallback, AfterEachCallback {
+
+    override fun beforeEach(context: ExtensionContext?) {
+        ArchTaskExecutor.getInstance()
+            .setDelegate(object : TaskExecutor() {
+                override fun executeOnDiskIO(runnable: Runnable) = runnable.run()
+
+                override fun postToMainThread(runnable: Runnable) = runnable.run()
+
+                override fun isMainThread(): Boolean = true
+            })
+    }
+
+    override fun afterEach(context: ExtensionContext?) {
+        ArchTaskExecutor.getInstance().setDelegate(null)
+    }
+}