### Question:
ValidableTextField extends TextField { public void setValidator(Validator<String> validator) { requireNotNullArg(validator, "Validator cannot be null for ValidableTextField"); validationSupport.setValidator(validator); } ValidableTextField();  ValidableTextField(String text); final ValidationState getValidationState(); final ReadOnlyObjectProperty<ValidationState> validProperty(); void setEnableInvalidStyle(final boolean active); void setErrorMessage(String message); void setOnEnterValidation(final boolean active); void setValidator(Validator<String> validator); void validate();  }### Answer:
@Test(expected = IllegalArgumentException.class) public void nullValidator() { victim.setValidator(null); }
@Test public void tooltip() { victim.setValidator(Validators.nonBlank()); clickOn(victim); push(KeyCode.TAB); sleep(500); assertTrue(robotContext().getWindowFinder().listWindows().size() > 1); }