@Test
public void neFailsWithBothValuesUnresolved() {

    when(expressionResolver.resolveAsPipelineElement("header:reply-to"))
            .thenReturn(PipelineElement.unresolved());
    when(expressionResolver.resolveAsPipelineElement("header:some-header"))
            .thenReturn(PipelineElement.unresolved());
    final String params = String.format("(%s,\"%s\",%s)", "header:reply-to", "ne", "header:some-header");
    assertThat(underTest.apply(KNOWN_INPUT, params, expressionResolver)).isEmpty();
}