query specification

query spec.cs

    /*
     * A query specification is intended to be used on a method with a return value. The
     * general idea is that the Given() will build the SUT. The when() will call the method
     * returning the methods return value. The expectations are then on the returned value.
     * 
     * You may wonder how you can assert on the sut after the call. You can't using this 
     * template. This is by design, see CQS by Bertrand Meyer, you should not mutate state
     * of the object when querying. If you want to break this rule use a more open template
     * and specialize it.
     */
    public class QuerySepcification
    {
        public ISpecification it_returns_something_interesting = new QuerySpecification<QueryExample, Product>()
        {
            On = () => new QueryExample(),
            When = obj => obj.GetProduct(14),
            Expect =
                {
                    product => product.Id == 14,
                    product => product.Code == "TEST",
                    product => product.Description == "test description"
                },
        };
    }

    public class QueryExample
    {
        public Product GetProduct(int id)
        {
            return new Product(id, "TEST", "test description");
        }
    }

    public class Product
    {
        public readonly int Id;
        public readonly string Code;
        public readonly string Description;

        public Product(int id, string code, string description)
        {
            Id = id;
            Description = description;
            Code = code;
        }
    }