public void InvalidArguments()
        {
            var aggregator = new AggregatorMock();
            var validator  = new AggregatorValidationDecorator(aggregator);

            Assert.Throws(typeof(AggregationException), () => validator.Get(new List <Person>(), new[] { "Ag" }, new[] { "Country" }, Aggregation));
            Assert.Throws(typeof(AggregationException), () => validator.Get(new List <Person>(), new string[] {}, new[] { "Country" }, Aggregation));
            Assert.Throws(typeof(AggregationException), () => validator.Get(new List <Person>(), null, new[] { "Country" }, Aggregation));
            Assert.Throws(typeof(AggregationException), () => validator.Get(new List <Person>(), new[] { "Age" }, new string[] {}, Aggregation));
            Assert.Throws(typeof(AggregationException), () => validator.Get(new List <Person>(), new[] { "Ag" }, null, Aggregation));
            Assert.Throws(typeof(AggregationException), () => validator.Get(new List <Person>(), new string[] {}, new string[] {}, Aggregation));
            Assert.Throws(typeof(AggregationException), () => validator.Get(new List <Person>(), null, null, Aggregation));
            Assert.Throws(typeof(AggregationException), () => validator.Get(new List <Person>(), new[] { "Age", "Age" }, new[] { "Country" }, Aggregation));
            Assert.Throws(typeof(AggregationException), () => validator.Get(new List <Person>(), new[] { "Age", "Country" }, new[] { "Country" }, Aggregation));
        }
        public void CommonCase()
        {
            var aggregator = new AggregatorMock();
            var validator  = new AggregatorValidationDecorator(aggregator);

            var result = validator.Get(new List <Person>(), new[] { "Age" }, new[] { "Country" }, Aggregation);

            Assert.Equal(result, aggregator.LastReturnValue);
            Assert.Equal(1, aggregator.CallCount);
        }