Replaced else statement with check for type Move

models/board.js

@@ -73,6 +73,10 @@ class Board {
     }
 
     applyMove(move) {
+        if( !(move instanceof Move) ) {
+            throw new Error('move must be an instanceof Move');
+        }
+
         if(this.getTile(move.x, move.y) !== Game.EmptyCell) {
             throw new Error('cell must be empty to apply move');
         }
@@ -84,9 +88,6 @@ class Board {
         else if( move.player === Game.PlayerO) {
             nextPlayer = Game.PlayerX;
         }
-        else {
-            throw new Error(`Unknown Player ${move.player}`);
-        }
 
         if (move.player !== this._currentTurn) {
             throw new Error(`The board's current player is ${this._currentTurn} but a move for player `+

test/board.js

@@ -320,6 +320,14 @@ describe('Board', () => {
     });
 
     describe('#applyMove', () => {
+        it('should throw an error with invalid parameters', () => {
+           const board = new Board();
+
+           expect(() => {
+               board.applyMove({x:1, y:1, player:1});
+           }).to.throw(Error, 'Move');
+        });
+
         it('should apply a valid move to an empty board.', () => {
             const board = new Board();
             const firstMove = new Move(1, 1, Game.PlayerX);