your test is too faraway from the method you suspect.

Your test is too faraway from the method isLegal() you suspect. You need write a unittest to test the methods when you suspect it is not working.

isLegal() is an implementation. I guess it is called in CardGameGUI somewhere. Check CardGameGUI If isLegal() has been actually called.

containsJQK() and containsPairSum11() are private. why you write them?

give me class Deck.