Adding a unit test

amazon-kinesis-client/src/main/java/software/amazon/kinesis/leases/LeaseCleanupManager.java

@@ -81,14 +81,16 @@ public class LeaseCleanupManager {
      * {@link LeaseCleanupManager#leaseCleanupIntervalMillis}
      */
     public void start() {
+        if (!isRunning) {
             log.debug("Starting lease cleanup thread.");
-
+            completedLeaseStopwatch.reset().start();
-        completedLeaseStopwatch.start();
+            garbageLeaseStopwatch.reset().start();
-        garbageLeaseStopwatch.start();
-
             deletionThreadPool.scheduleAtFixedRate(new LeaseCleanupThread(), INITIAL_DELAY, leaseCleanupIntervalMillis,
                     TimeUnit.MILLISECONDS);
             isRunning = true;
+        } else {
+            log.debug("Lease cleanup thread already running, no need to start.");
+        }
     }
 
     /**

amazon-kinesis-client/src/test/java/software/amazon/kinesis/leases/LeaseCleanupManagerTest.java

@@ -15,6 +15,7 @@
 
 package software.amazon.kinesis.leases;
 
+import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -83,6 +84,16 @@ public class LeaseCleanupManagerTest {
         when(leaseCoordinator.updateLease(any(Lease.class), any(UUID.class), any(String.class), any(String.class))).thenReturn(true);
     }
 
+    /**
+     * Tests subsequent calls to start {@link LeaseCleanupManager}.
+     */
+    @Test
+    public final void testSubsequentStarts() {
+        leaseCleanupManager.start();
+        Assert.assertTrue(leaseCleanupManager.isRunning());
+        leaseCleanupManager.start();
+    }
+
     /**
      * Tests that when both child shard leases are present, we are able to delete the parent shard for the completed
      * shard case.