Create an instance of the Board class and use putShape(Shape aShape, int rowPos, int colPos) to place a Cross or Circle shape on the board. Use checkForWinners(Shape aShape) after placing a shape on the board to check if the game is over, this method returns true if any column, row or diagonal has shapes equal to aShape in every cell. When every position of the board is taken by a shape, isFilled() returns true. Also, you can check if the shape was placed on the board with placedOnBoard().
Every time you want to place a shape on the board, you need to create a new instance of that shape class, you cannot re-use the same object. The default size of the board is 3x3 and a valid position is (row,column) where row = 0,1,2 and column=0,1,2.
Once you've cloned the project, in order to run the tests, you should go to the tic-tac-toe/ folder and issue the following command:
mvn test
The following snippet shows an example of how to place a Cross shape on the top left corner of the board.
Board board = new Board();
Shape cross = new Cross();
board.putShape(cross, 0, 0);
boolean placedOnBoard = cross.placedOnBoard();
boolean crossShapeHasWon = board.checkForWinner(cross);
boolean boardCompletelyFilled = board.isFilled();