One of the easiest to understand imo

The current use of "assertEquals" is as follows: assertEquals(Groups.groupCheck("({"), false);

That is incorrect. The method is defined as assertEquals(expected, actual).

The implementation has it reversed. So if my groupCheck method returned true instead of the desired false I would get the following message:

"expected:true but was:false" When the message should be "expected:false but was:true"

I suggest correcting the use of assertEquals in the Test Cases in order to give developers more accurate feedback.