Fix tests where coroutine outlive the test body (#4342)

Author: dkhalanskyjb

kotlinx-coroutines-core/common/test/ParentCancellationTest.kt

@@ -158,6 +158,7 @@ class ParentCancellationTest : TestBase() {
         }
         if (expectParentActive) {
             assertTrue(parent.isActive)
+            parent.cancelAndJoin()
         } else {
             parent.join()
             assertFalse(parent.isActive)

kotlinx-coroutines-core/jvm/test/scheduling/BlockingCoroutineDispatcherTerminationStressTest.kt

@@ -19,14 +19,18 @@ class BlockingCoroutineDispatcherTerminationStressTest : TestBase() {
         baseDispatcher.close()
     }
 
+    /**
+     * Tests that when threads are created to accommodate the new tasks, but then don't receive any tasks for the
+     * duration of their terminate-on-idling timeout, liveness does not suffer.
+     */
     @Test
-    fun testTermination() {
+    fun testTermination() = runTest {
         val rnd = Random()
         val deadline = System.currentTimeMillis() + TimeUnit.SECONDS.toMillis(TEST_SECONDS)
         while (System.currentTimeMillis() < deadline) {
             Thread.sleep(rnd.nextInt(30).toLong())
             repeat(rnd.nextInt(5) + 1) {
-                GlobalScope.launch(ioDispatcher) {
+                launch(ioDispatcher) {
                     Thread.sleep(rnd.nextInt(5).toLong())
                 }
             }