@Test
public void someProductMissingSomeProductNotExpected() throws Exception {

    requiredProductsInCart("900901", "900902", "900903", "900904");
    RegisterNew command = givenCartRegistrationCommand("9009XXXX", "900902", "900903", "900904");
    ValidationResult result = validator.validate(command);
    Assertions.assertThat(result.getViolations())
            .contains(
                    "not expected refNo 9009XXXX",
                    "refNo 900901 expected in pocket 1, but not found");
}