2 files changed, 122 insertions, 0 deletions
diff --git a/board.rb b/board.rb
index df66a8d..4bef0d3 100644
--- a/board.rb
+++ b/board.rb
@@ -33,5 +33,43 @@ class Board
   end
   
   def winner?
+    initial = '.'
+    
+    # Check horizontal
+    @board.each do |row|
+      return row[0] if array_items_equal(row) and row[0] != initial
+    end
+    
+    # Check vertical
+    @board.transpose.each do |column|
+      return column[0] if array_items_equal(column) and column[0] != initial
+    end
+    
+    # Check diagonals
+    descending = [
+      @board[0][0],
+      @board[1][1],
+      @board[2][2]
+    ]
+    if array_items_equal(descending) and descending[0] != initial
+      return descending[0]
+    end
+    
+    ascending = [
+      @board[2][0],
+      @board[1][1],
+      @board[0][2]
+    ]
+    if array_items_equal(ascending) and ascending[0] != initial
+      return ascending[0]
+    end
+    
+    nil
   end
+  
+  private
+  
+    def array_items_equal(arr)
+      arr.uniq.length == 1
+    end
 end
diff --git a/spec/board_spec.rb b/spec/board_spec.rb
index 09f50e1..70caa81 100644
--- a/spec/board_spec.rb
+++ b/spec/board_spec.rb
@@ -59,5 +59,89 @@ EOF
   end
   
   describe '#winner?' do
+    before do
+      @board = Board.new
+    end
+    
+    it 'must be nil when no player has won' do
+      @board.winner?.must_be_nil
+    end
+    
+    it 'must be the winning player' do
+    end
+    
+    it 'counts horizontal matches as wins' do
+      @board.instance_variable_set(:@board, [
+        ['X', 'X', 'X'],
+        ['X', 'O', 'O'],
+        ['O', 'X', 'O'],
+      ])
+      @board.winner?.must_equal 'X'
+      
+      @board.instance_variable_set(:@board, [
+        ['X', 'O', 'X'],
+        ['O', 'O', 'O'],
+        ['O', 'X', 'X'],
+      ])
+      @board.winner?.must_equal 'O'
+      
+      @board.instance_variable_set(:@board, [
+        ['O', 'X', 'X'],
+        ['X', 'O', 'X'],
+        ['O', 'O', 'O'],
+      ])
+      @board.winner?.must_equal 'O'
+    end
+    
+    it 'counts vertical matches as wins' do
+      @board.instance_variable_set(:@board, [
+        ['X', 'O', 'X'],
+        ['X', 'O', 'O'],
+        ['X', 'X', 'O'],
+      ])
+      @board.winner?.must_equal 'X'
+      
+      @board.instance_variable_set(:@board, [
+        ['X', 'O', 'X'],
+        ['X', 'O', 'O'],
+        ['O', 'O', 'X'],
+      ])
+      @board.winner?.must_equal 'O'
+      
+      @board.instance_variable_set(:@board, [
+        ['O', 'X', 'X'],
+        ['X', 'O', 'X'],
+        ['O', 'O', 'X'],
+      ])
+      @board.winner?.must_equal 'X'
+    end
+    
+    it 'counts diagonal matches as wins' do
+      @board.instance_variable_set(:@board, [
+        ['O', 'X', 'X'],
+        ['X', 'O', 'O'],
+        ['O', 'X', 'O'],
+      ])
+      @board.winner?.must_equal 'O'
+      
+      @board.instance_variable_set(:@board, [
+        ['X', 'O', 'X'],
+        ['O', 'X', 'O'],
+        ['O', 'X', 'X'],
+      ])
+      @board.winner?.must_equal 'X'
+    end
+  end
+  
+  describe '#array_items_equal' do
+    it 'is true when all elements in the array are equal' do
+      Board.new.send(:array_items_equal,
+        ['X', 'X', 'X', 'X', 'X', 'X', 'X']).must_equal true
+    end
+    
+    it 'is false when any element is not equal to the rest' do
+      Board.new.send(:array_items_equal,
+        ['X', 'O', 'X', 'X', 'X', 'X', 'X']).must_equal false
+    end
   end
 end