public void Returns_value_from_LongValueRetriever_when_passed_not_empty_string()
        {
            Func<string, long> func = v =>
            {
                if (v == "test value") return 123;
                if (v == "another test value") return 456;
                return 0;
            };

            var retriever = new NullableLongValueRetriever(func);
            retriever.GetValue("test value").ShouldEqual(123);
            retriever.GetValue("another test value").ShouldEqual(456);
        }
 public void Returns_null_when_passed_empty_string()
 {
     var retriever = new NullableLongValueRetriever(v => 3);
     retriever.GetValue(string.Empty).ShouldBeNull();
 }
 public void Returns_null_when_the_value_is_null()
 {
     var retriever = new NullableLongValueRetriever(v => 0);
     retriever.GetValue(null).ShouldBeNull();
 }