Enhance testing of all methods

[ryan597]

Is your feature request related to a problem? Please describe

Need more tests for current functions, and the planned functionality to start a test driven development.

Describe the solution you'd like

Reach 100% code coverage

• Tests for Board methods #15
• Tests for Piece methods #16
• Tests for Square methods #17
• Tests for Player methods #18

Additional context

Add any other context or screenshots about the feature request here.