@Test
 public void canRemoveAttributeByNonExistingNamespaceAndName() {
   element.removeAttrNs(NON_EXISTING, "order");
   assertThat(element.hasAttrNs(NON_EXISTING, "order")).isFalse();
 }
 @Test
 public void canRemoveAttributeByNullNamespaceAndName() {
   element.removeAttrNs(null, "order");
   assertThat(element.hasAttrNs(null, "order")).isFalse();
 }
 @Test(expected = IllegalArgumentException.class)
 public void cannotRemoveAttributeByNamespaceAndNullName() {
   element.removeAttrNs(EXAMPLE_NAMESPACE, null);
 }
 @Test
 public void canRemoveAttributeByNamespaceAndName() {
   element.removeAttrNs(EXAMPLE_NAMESPACE, "order");
   assertThat(element.hasAttrNs(EXAMPLE_NAMESPACE, "order")).isFalse();
 }