code: @Nonnull
      private static RuleEvaluator makeRuleEvaluator(final ExpressionFactory expressionFactory, final FunctionMapper functionMapper) {
          // Make the expression evaluation context.
          final Map<String, Object> testConstants = Collections.emptyMap();
  
          return new RuleEvaluator(expressionFactory, functionMapper, testConstants);
      }
docs: TODO(pwp): add some test constants?