private RankingExpression assertEvaluates(Value value, String expressionString, Context context) {
        try {
            RankingExpression expression = new RankingExpression(expressionString);
            assertEquals(expression.toString(), value, expression.evaluate(context));
            return expression;
        }
        catch (ParseException e) {
            throw new RuntimeException(e);
        }
    }
"XOR" neural network, separate expression per layer
searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/evaluation/NeuralNetEvaluationTestCase.java