Luke.cs

namespace TechList
{
    [TestFixture]
    public class Luke
    {
        class DemoObject
        {
            public string GroupId { get; set; }
            public int GroupCount { get; set; }
        }

        static bool AreThereAnyErrors(IEnumerable<DemoObject> input)
        {
            return input
                .GroupBy(obj => obj.GroupId)
                .Where(group => group
                    .Any(groupItem => groupItem.GroupCount != group.Count()))
                .Any();
        }

        [Test]
        public void AreThereAnyErrors_ReturnsTrueWhenAnEntireGroupHasWrongCount()
        {
            // Arrange
            var input = new[] {
                new DemoObject { GroupId = "A", GroupCount = 2 },
                new DemoObject { GroupId = "B", GroupCount = 1 },
                new DemoObject { GroupId = "A", GroupCount = 2 },
                new DemoObject { GroupId = "C", GroupCount = 1 },
                new DemoObject { GroupId = "A", GroupCount = 2 }
            };

            // Act
            var result = AreThereAnyErrors(input);

            // Assert
            Assert.IsTrue(result);
        }

        [Test]
        public void AreThereAnyErrors_ReturnsTrueWhenOneElementOfAGroupHasWrongCount()
        {
            // Arrange
            var input = new[] {
                new DemoObject { GroupId = "A", GroupCount = 3 },
                new DemoObject { GroupId = "B", GroupCount = 1 },
                new DemoObject { GroupId = "A", GroupCount = 2 },
                new DemoObject { GroupId = "C", GroupCount = 1 },
                new DemoObject { GroupId = "A", GroupCount = 3 }
            };

            // Act
            var result = AreThereAnyErrors(input);

            // Assert
            Assert.IsTrue(result);
        }

        [Test]
        public void AreThereAnyErrors_ReturnsFalseWhenAllGroupsHaveCorrectCount()
        {
            // Arrange
            var input = new[] {
                new DemoObject { GroupId = "A", GroupCount = 3 },
                new DemoObject { GroupId = "B", GroupCount = 1 },
                new DemoObject { GroupId = "A", GroupCount = 3 },
                new DemoObject { GroupId = "C", GroupCount = 1 },
                new DemoObject { GroupId = "A", GroupCount = 3 }
            };

            // Act
            var result = AreThereAnyErrors(input);

            // Assert
            Assert.IsFalse(result);
        }
    }
}