Using the CollectionAssert class in a C# unit test

Unit testing with collections can be tricky, especially when you’re trying to compare collections. Enter the lowly ‘CollectionAssert’ class in C#:

//  Assert:
//  1.) These items are not null
//  2.) These items are of type MyClass
//  3.) The expected collection is the same as the actual collection
CollectionAssert.AllItemsAreNotNull(actual);
CollectionAssert.AllItemsAreInstancesOfType(actual, typeof(MyClass));
CollectionAssert.AreEqual(expected, actual);
        
//  Also:
//  4.) The collection we expect to be filled shouldn't be the same as the empty one
//  5.) The expected empty collection should be the same as the actual empty one
CollectionAssert.AreNotEqual(expected, actualEmpty);
CollectionAssert.AreEqual(expectedEmpty, actualEmpty);