HBASE-22615 Make TestChoreService more robust to timing

* phrase fudge factor "deltas" in terms of the original period
* increase the delta allowed for chore timing from 5% to 20%
* improve some assertions

Closes #328

Signed-off-by: Reid Chan <reidchan@apache.org>
Signed-off-by: Sakthi <sakthivel.azhaku@gmail.com>
(cherry picked from commit 9aee88e)

Author: busbey

hbase-common/src/test/java/org/apache/hadoop/hbase/TestChoreService.java

@@ -345,17 +345,17 @@ public void testChoreServiceConstruction() throws InterruptedException {
   public void testFrequencyOfChores() throws InterruptedException {
     final int period = 100;
     // Small delta that acts as time buffer (allowing chores to complete if running slowly)
-    final int delta = 5;
+    final int delta = period/5;
     ChoreService service = new ChoreService("testFrequencyOfChores");
     CountingChore chore = new CountingChore("countingChore", period);
     try {
       service.scheduleChore(chore);
 
       Thread.sleep(10 * period + delta);
-      assertTrue(chore.getCountOfChoreCalls() == 11);
+      assertEquals("10 periods have elapsed.", 11, chore.getCountOfChoreCalls());
 
-      Thread.sleep(10 * period);
-      assertTrue(chore.getCountOfChoreCalls() == 21);
+      Thread.sleep(10 * period + delta);
+      assertEquals("20 periods have elapsed.", 21, chore.getCountOfChoreCalls());
     } finally {
       shutdownService(service);
     }
@@ -371,14 +371,14 @@ public void shutdownService(ChoreService service) throws InterruptedException {
   @Test (timeout=20000)
   public void testForceTrigger() throws InterruptedException {
     final int period = 100;
-    final int delta = 10;
+    final int delta = period/10;
     ChoreService service = new ChoreService("testForceTrigger");
     final CountingChore chore = new CountingChore("countingChore", period);
     try {
       service.scheduleChore(chore);
       Thread.sleep(10 * period + delta);
 
-      assertTrue(chore.getCountOfChoreCalls() == 11);
+      assertEquals("10 periods have elapsed.", 11, chore.getCountOfChoreCalls());
 
       // Force five runs of the chore to occur, sleeping between triggers to ensure the
       // chore has time to run
@@ -393,12 +393,14 @@ public void testForceTrigger() throws InterruptedException {
       chore.triggerNow();
       Thread.sleep(delta);
 
-      assertTrue("" + chore.getCountOfChoreCalls(), chore.getCountOfChoreCalls() == 16);
+      assertEquals("Trigger was called 5 times after 10 periods.", 16,
+          chore.getCountOfChoreCalls());
 
       Thread.sleep(10 * period + delta);
 
       // Be loosey-goosey. It used to be '26' but it was a big flakey relying on timing.
-      assertTrue("" + chore.getCountOfChoreCalls(), chore.getCountOfChoreCalls() > 16);
+      assertTrue("Expected at least 16 invocations, instead got " + chore.getCountOfChoreCalls(),
+          chore.getCountOfChoreCalls() > 16);
     } finally {
       shutdownService(service);
     }
@@ -410,7 +412,7 @@ public void testCorePoolIncrease() throws InterruptedException {
     ChoreService service = new ChoreService("testCorePoolIncrease", initialCorePoolSize, false);
 
     try {
-      assertEquals("Should have a core pool of size: " + initialCorePoolSize, initialCorePoolSize,
+      assertEquals("Setting core pool size gave unexpected results.", initialCorePoolSize,
         service.getCorePoolSize());
 
       final int slowChorePeriod = 100;
@@ -694,7 +696,7 @@ public void testStopperForScheduledChores() throws InterruptedException {
     Stoppable stopperForGroup1 = new SampleStopper();
     Stoppable stopperForGroup2 = new SampleStopper();
     final int period = 100;
-    final int delta = 10;
+    final int delta = period/10;
 
     try {
       ScheduledChore chore1_group1 = new DoNothingChore("c1g1", stopperForGroup1, period);