Add playground for testing coroutines

Author: LukasLechnerDev

app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/playground/testing/1_testing_coroutines.kt

@@ -0,0 +1,43 @@
+package com.lukaslechner.coroutineusecasesonandroid.playground.testing
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.test.runBlockingTest
+import org.junit.Test
+
+
+class SystemUnderTest {
+
+    suspend fun functionWithDelay(): Int {
+        delay(1000)
+        return 42
+    }
+}
+
+fun CoroutineScope.functionThatStartsNewCoroutine() {
+    launch {
+        delay(1000)
+        println("Coroutine completed!")
+    }
+}
+
+class TestClass {
+
+    @Test
+    fun `functionWithDelay should return 42`() = runBlockingTest {
+
+        val realTimeStart = System.currentTimeMillis()
+        val virtualTimeStart = currentTime
+
+        functionThatStartsNewCoroutine()
+        advanceTimeBy(1000)
+
+        val realTimeDuration = System.currentTimeMillis() - realTimeStart
+        val virtualTimeDuration = currentTime - virtualTimeStart
+
+        println("Test took $realTimeDuration real ms")
+        println("Test took $virtualTimeDuration virtual ms")
+    }
+
+}