Added tests for thread-pool pattern

Fixed concurrency problem in id generation of Task

thread-pool/src/test/java/com/iluwatar/threadpool/WorkerTest.java

@@ -0,0 +1,31 @@
+package com.iluwatar.threadpool;
+
+import org.junit.Test;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.verifyZeroInteractions;
+
+/**
+ * Date: 12/30/15 - 18:21 PM
+ *
+ * @author Jeroen Meulemeester
+ */
+public class WorkerTest {
+
+  /**
+   * Verify if a worker does the actual job
+   */
+  @Test
+  public void testRun() {
+    final Task task = mock(Task.class);
+    final Worker worker = new Worker(task);
+    verifyZeroInteractions(task);
+
+    worker.run();
+    verify(task).getTimeMs();
+    verifyNoMoreInteractions(task);
+  }
+
+}