Maybe I'm missing something, but I don't think this solution is valid. It throws an ArgumentNullException on AddRange if the rectangle becomes a square.

I believe arraysSimilar([1,2], [0,3]) should return false. There are some solutions that pass the other tests, but not this one.

The above code is still incorrectly accepted. The following test case should reject the above answer:

Test.expect(!validPhoneNumber("a(123) 456-78900"));