fix: Deflake WaiterTest (#2600)

* chore: Deflake WaiterTest

* chore: Update test

* chore: Test specific case

* fix: Update WaiterTest

* fix: Fix flaky test

* fix: Try more fixes

* fix: Simplify WaiterTest logic and removing special testing on Kokoro config

Author: michaelpri10

google-cloud-pubsub/src/test/java/com/google/cloud/pubsub/v1/WaiterTest.java

@@ -55,39 +55,61 @@ public void run() {
   }
 
   @Test
-  public void testTryWait_Completes() {
+  public void testTryWait_Completes() throws Exception {
     final Waiter waiter = new Waiter();
     waiter.incrementPendingCount(1);
     final FakeClock clock = new FakeClock();
 
+    final Thread mainThread = Thread.currentThread();
     Thread t =
         new Thread(
-            () -> {
-              try {
-                Thread.sleep(100);
-              } catch (InterruptedException e) {
+            new Runnable() {
+              @Override
+              public void run() {
+                while (mainThread.getState() == Thread.State.NEW) {
+                  Thread.yield();
+                }
+                waiter.incrementPendingCount(-1);
               }
-              waiter.incrementPendingCount(-1);
             });
     t.start();
 
     assertTrue(waiter.tryWait(500, clock));
+    t.join();
+
+    assertEquals(0, waiter.pendingCount());
   }
 
   @Test
-  public void testTryWait_TimesOut() {
+  public void testTryWait_TimesOut() throws Exception {
     final Waiter waiter = new Waiter();
     waiter.incrementPendingCount(1);
     final FakeClock clock = new FakeClock();
 
+    final Thread mainThread = Thread.currentThread();
     Thread t =
         new Thread(
-            () -> {
-              clock.advance(100, TimeUnit.MILLISECONDS);
+            new Runnable() {
+              @Override
+              public void run() {
+                while (mainThread.getState() == Thread.State.NEW) {
+                  Thread.yield();
+                }
+                try {
+                  // Waits some additional time to ensure that the waiter is actually waiting.
+                  Thread.sleep(100);
+                  clock.advance(200, TimeUnit.MILLISECONDS);
+                } catch (InterruptedException e) {
+                  // Ignored.
+                }
+              }
             });
     t.start();
 
     assertFalse(waiter.tryWait(100, clock));
+    t.join();
+
+    assertEquals(1, waiter.pendingCount());
   }
 
   @Test