Elaborate: add forward/backward movement

mars-rover/src/rover.py

@@ -1,6 +1,7 @@
 class Rover:
 
     global commands
+    global deltas
 
     def __init__(self, x, y, orientation):
         self.x = x
@@ -10,17 +11,30 @@ def __init__(self, x, y, orientation):
     def move(self, commands):
         self.moveBy(commands[0])
 
+    # use command pattern and lookup to avoid switch statements :)
     def moveBy(self, commandKey):
         command = commands[commandKey]
-        command(self)
+        delta = deltas[self.orientation]
+        command(self, delta)
 
-    def move_forward(self):
-        self.y += 1
+    def move_forward(self, delta):
+        self.x += delta[0]
+        self.y += delta[1]
 
-    def move_backward(self):
-        self.y -= 1
+    def move_backward(self, delta):
+        self.x -= delta[0]
+        self.y -= delta[1]
 
+    # commands to dispatch for each move key
     commands = {
         'f': move_forward,
         'b': move_backward
     }
+
+    # x,y deltas to move forward for each orientation
+    deltas = {
+        'N': [ +0, +1 ],
+        'S': [ +0, -1 ],
+        'E': [ +1, +0 ],
+        'W': [ -1, +0 ]
+    }

mars-rover/test/test_rover.py

@@ -16,6 +16,12 @@ def test_initial_y(self):
     def test_initial_orientation(self):
         assert_equal('N', r.orientation)
 
+class TestMovesOrientationNorth:
+
+    def setup(self):
+        global r
+        r = rover.Rover(10, 21, 'N')
+
     def test_move_f(self):
         r.move(list("f"))
         assert_equal(22, r.y)
@@ -25,3 +31,53 @@ def test_move_b(self):
         r.move(list("b"))
         assert_equal(10, r.x)
         assert_equal(20, r.y)
+
+class TestMovesOrientationSouth:
+
+    def setup(self):
+        # tried using self.r, but it gets too wordy using self.r everywhere
+        global r
+        r = rover.Rover(10, 21, 'S')
+
+    def test_move_forward(self):
+        r.move(list("f"))
+        assert_equal(10, r.x)
+        assert_equal(20, r.y)
+
+    def test_move_backward(self):
+        r.move(list("b"))
+        assert_equal(10, r.x)
+        assert_equal(22, r.y)
+
+# would love use use test generators!
+class TestMovesOrientationEast:
+
+    def setup(self):
+        global r
+        r = rover.Rover(10, 21, 'E')
+
+    def test_move_forward(self):
+        r.move(list('f'))
+        assert_equal(11, r.x)
+        assert_equal(21, r.y)
+
+    def test_move_backward(self):
+        r.move(list("b"))
+        assert_equal(9, r.x)
+        assert_equal(21, r.y)
+
+class TestMovesOrientationWest:
+
+    def setup(self):
+        global r
+        r = rover.Rover(10, 21, 'W')
+
+    def test_move_forward(self):
+        r.move(list("f"))
+        assert_equals(9, r.x)
+        assert_equals(21, r.y)
+
+    def test_move_backward(self):
+        r.move(list("b"))
+        assert_equal(11, r.x)
+        assert_equal(21, r.y)