@Test
public void testInvalidHeaderMappingThrowsException() {

    final Map<String, String> mapping = new HashMap<>(TestConstants.HEADER_MAPPING.getMapping());
    mapping.put("thingId", "{{ thing:invalid }}");
    final Source source = newSourceBuilder()
            .headerMapping(ConnectivityModelFactory.newHeaderMapping(mapping))
            .build();
    Assertions.assertThatExceptionOfType(ConnectionConfigurationInvalidException.class)
            .isThrownBy(() -> UNDER_TEST.validateSource(source, DittoHeaders.empty(), () -> "testSource"))
            .withCauseInstanceOf(UnresolvedPlaceholderException.class);
}