@Test
 public void testMessageConstructor() {
   String message = "message";
   try {
     throw new ZapClientException(message);
   } catch (ZapClientException e) {
     assertEquals(e.getMessage(), message);
   }
 }
 @Test
 public void testThrowableConstructor() {
   Throwable throwable = new NullPointerException("test");
   try {
     throw new ZapClientException(throwable);
   } catch (ZapClientException e) {
     assertEquals(e.getCause(), throwable);
   }
 }
 @Test
 public void testMessageAndThrowableConstructor() {
   String message = "message";
   Throwable throwable = new NullPointerException("test");
   try {
     throw new ZapClientException(message, throwable);
   } catch (ZapClientException e) {
     assertEquals(e.getMessage(), message);
     assertEquals(e.getCause(), throwable);
   }
 }