@Test
public void testValidatorDoesNotExist() {

  when(validatorFactory.get("someValidator", "someParameter")).thenThrow(IllegalArgumentException.class);
  InvalidArgumentException ex = assertThrows(
    InvalidArgumentException.class,
    () -> validatorHandler.assertValidatorExists("someValidator", "someParameter")
  );
  assertEquals(
    SetUtils.set("validator.not.exist"),
    SetUtils.set(ex.getValidationErrors(), InvalidArgumentException.ValidationError::getMessageTemplate));
}