marksim · October 30, 2013 03:23 · Oct 30, 2013
diff --git a/tic_tac_toe_spec.rb b/tic_tac_toe_spec.rb
@@ -0,0 +1,112 @@
+require 'rspec'
+require 'set'
+
+class TicTacToe
+  attr_reader :current_player
+
+  def initialize
+    @current_player = 'O'
+    @plays = {
+      'O' => [],
+      'X' => [],
+    }
+  end
+
+  def at(x, y)
+    @plays.keys.each do |player|
+      return player if @plays[player].include?([x, y])
+    end
+    nil
+  end
+
+  def play(x, y)
+    raise OutOfBoundsException if x.abs > 1 || y.abs > 1
+    return if at(x, y)
+    @plays[@current_player] << [x,y]
+    # toggle current player
+    @current_player = @current_player == 'O' ? 'X' : 'O'
+  end
+
+  def winner
+    @plays.keys.each do |player|
+      (-1..1).each do |index|
+        return player if @plays[player].select {|tuple| tuple.first == index}.count == 3
+        return player if @plays[player].select {|tuple| tuple.last == index}.count == 3
+        return player if @plays[player].select {|tuple| tuple.last == tuple.first}.count == 3
+        return player if @plays[player].select {|tuple| tuple.last == (-1 * tuple.first)}.count == 3
+      end
+    end
+    nil
+  end
+end
+
+class OutOfBoundsException < Exception; end
+
+
+describe 'TicTacToe' do
+  subject(:game) { TicTacToe.new }
+
+  it "lets the players take turns placing markers" do
+    expect(game.at(0, 0)).to be_nil
+    game.play(0, 0)
+    expect(game.at(0, 0)).to eql 'O'
+    game.play(1, 1)
+    expect(game.at(1, 1)).to eql 'X'
+  end
+  it "won't let a player play outside the board (3x3)?" do
+    expect { game.play(-2, 0) }.to raise_error(OutOfBoundsException)
+    expect { game.play(0, 2) }.to raise_error(OutOfBoundsException)
+    expect { game.play(-2, -5) }.to raise_error(OutOfBoundsException)
+  end
+  it "does not let a player place a marker in a taken space" do
+    game.play(0, 0)
+    expect(game.at(0, 0)).to eql 'O'
+    game.play(0, 0)
+    expect(game.at(0, 0)).to eql 'O'
+  end
+  it "does not advance the current player after an invalid play" do
+    game.play(0, 0)
+    expect(game.current_player).to eql 'X'
+    game.play(0, 0)
+    expect(game.current_player).to eql 'X'
+  end
+
+  context "winning" do
+    it "is won when one player has 3 in a row vertically" do
+      expect(game.winner).to be_nil
+      game.play(0, 0) # O
+      game.play(-1, -1) # X
+      game.play(0, -1) # O
+      game.play(1, 1) # X
+      game.play(0, 1) # O
+      expect(game.winner).to eql 'O'
+    end
+    it "is won when one player has 3 in a row horizontally" do
+      expect(game.winner).to be_nil
+      game.play(0, 0) # O
+      game.play(-1, -1) # X
+      game.play(-1, 0) # O
+      game.play(1, 1) # X
+      game.play(1, 0) # O
+      expect(game.winner).to eql 'O'
+    end
+    it "is won when one player has 3 in a row diagonally from right to left" do
+      expect(game.winner).to be_nil
+      game.play(0, 0) # O
+      game.play(-1, 0) # X
+      game.play(-1, -1) # O
+      game.play(0, 1) # X
+      game.play(1, 1) # O
+      expect(game.winner).to eql 'O'
+    end
+    it "is won when one player has 3 in a row diagonally from left to right" do
+      expect(game.winner).to be_nil
+      game.play(0, 0) # O
+      game.play(-1, 0) # X
+      game.play(-1, 1) # O
+      game.play(0, 1) # X
+      game.play(1, -1) # O
+      expect(game.winner).to eql 'O'
+    end
+  end
+end