PipelineFunctionFilter implements PipelineFunction { @Override public Signature getSignature() { return FilterFunctionSignature.INSTANCE; }  @Override String getName(); @Override Signature getSignature(); @Override PipelineElement apply(final PipelineElement value, final String paramsIncludingParentheses,
            final ExpressionResolver expressionResolver);  }
@Test public void getSignature() { final List<PipelineFunction.ParameterDefinition> parameterDefinitions = underTest.getSignature().getParameterDefinitions(); assertThat(parameterDefinitions).hasSize(3); assertThat(parameterDefinitions.get(0).getName()).isEqualTo("filterValue"); assertThat(parameterDefinitions.get(0).getType()).isEqualTo(String.class); assertThat(parameterDefinitions.get(1).getName()).isEqualTo("rqlFunction"); assertThat(parameterDefinitions.get(1).getType()).isEqualTo(String.class); assertThat(parameterDefinitions.get(2).getName()).isEqualTo("comparedValue"); assertThat(parameterDefinitions.get(2).getType()).isEqualTo(String.class); }