@Test
public void tryToAcceptNullValue() {

    final DittoHeaderDefinition headerDefinition = DittoHeaderDefinition.REQUESTED_ACKS;
    final JsonArrayValueValidator underTest = JsonArrayValueValidator.getInstance();
    assertThatExceptionOfType(DittoHeaderInvalidException.class)
            .isThrownBy(() -> underTest.accept(headerDefinition, null))
            .withMessageContaining("null")
            .withMessageContaining(headerDefinition.getKey())
            .withMessageEndingWith("is not a valid JsonArray.")
            .withNoCause();
}