FormGroup implements IsElement { public void clearValidationState() { Arrays.stream(ValidationState.values()).forEach(v -> removeCSSClass(div, v.getCssName())); }  void clearValidationState(); void setValidationState(final ValidationState state); @Override HTMLElement getElement();  }
@Test public void testClearValidationState() { when(domTokenList.contains(anyString())).thenReturn(true); formGroup.clearValidationState(); for (ValidationState v : ValidationState.values()) { verify(domTokenList).remove(v.getCssName()); } }