Fix RecoveryCoordinatorTest

Use new instance of RecoveryCoordinator in each test. Otherwise, the timestamp
of the next call to isTooSoon() could happen well after the backoff threshold
on slow machines (such as small nodes on Cloudbees Jenkins), causing false
test failures.

This also renames and refines the individual tests.

(cherry picked from commit 409ba25)

logback-core/src/test/java/ch/qos/logback/core/recovery/RecoveryCoordinatorTest.java

@@ -19,40 +19,61 @@
 
 public class RecoveryCoordinatorTest {
 
-  RecoveryCoordinator rc = new RecoveryCoordinator();
-  long now = System.currentTimeMillis();
+  @Test
+  public void recoveryNotNeededAfterInit() {
+    RecoveryCoordinator rc = new RecoveryCoordinator();
+    assertTrue(rc.isTooSoon());
+  }
 
   @Test
-  public void actualTime() throws InterruptedException {
+  public void recoveryNotNeededIfAsleepForLessThanBackOffTime() throws InterruptedException {
+    RecoveryCoordinator rc = new RecoveryCoordinator();
+    Thread.sleep(RecoveryCoordinator.BACKOFF_COEFFICIENT_MIN / 2);
     assertTrue(rc.isTooSoon());
-    Thread.sleep(RecoveryCoordinator.BACKOFF_COEFFICIENT_MIN+20);
+  }
+
+  @Test
+  public void recoveryNeededIfAsleepForMoreThanBackOffTime() throws InterruptedException {
+    RecoveryCoordinator rc = new RecoveryCoordinator();
+    Thread.sleep(RecoveryCoordinator.BACKOFF_COEFFICIENT_MIN + 20);
     assertFalse(rc.isTooSoon());
   }
-
+
+  @Test
+  public void recoveryNotNeededIfCurrentTimeSetToBackOffTime() throws InterruptedException {
+    RecoveryCoordinator rc = new RecoveryCoordinator();
+    long now = System.currentTimeMillis();
+    rc.setCurrentTime(now + RecoveryCoordinator.BACKOFF_COEFFICIENT_MIN);
+    assertTrue(rc.isTooSoon());
+  }
+
   @Test
-  public void smoke() {
-    // if the machine is really too busy or too slow, rc.isTooSoon can
-    // return false, hence we comment out the next line
-    // assertTrue(rc.isTooSoon());
-    rc.setCurrentTime(now+RecoveryCoordinator.BACKOFF_COEFFICIENT_MIN+1);
+  public void recoveryNeededIfCurrentTimeSetToExceedBackOffTime() {
+    RecoveryCoordinator rc = new RecoveryCoordinator();
+    long now = System.currentTimeMillis();
+    rc.setCurrentTime(now + RecoveryCoordinator.BACKOFF_COEFFICIENT_MIN + 1);
     assertFalse(rc.isTooSoon());
   }
-  
+
   @Test
-  public void longTermFailure() {
+  public void recoveryConditionDetectedEvenAfterReallyLongTimesBetweenRecovery() {
+    // Since backoff time quadruples whenever recovery is needed,
+    // we double the offset on each for-loop iteration, causing
+    // every other iteration to trigger recovery.
+
+    RecoveryCoordinator rc = new RecoveryCoordinator();
+    long now = System.currentTimeMillis();
     long offset = RecoveryCoordinator.BACKOFF_COEFFICIENT_MIN;
-    int tooSoonCount = 0;
-    for(int i = 0; i < 16; i++) {
-      rc.setCurrentTime(now+offset);
-
-      if(rc.isTooSoon()) {
-        System.out.println("isTooSoon successful at "+(offset));
-        tooSoonCount++;
+
+    for (int i = 0; i < 16; i++) {
+      rc.setCurrentTime(now + offset);
+
+      if (i % 2 == 0) {
+        assertTrue("recovery should've been needed at " + offset, rc.isTooSoon());
       } else {
-        //System.out.println("is NOT too soon at "+(offset));
-    }
+        assertFalse("recovery should NOT have been needed at " + offset, rc.isTooSoon());
+      }
       offset *= 2;
     }
-    assertEquals(8, tooSoonCount);
   }
 }