Added stack challenge.

stacks_queues/stack/test_stack.py

@@ -0,0 +1,41 @@
+from nose.tools import assert_equal
+
+
+class TestStack(object):
+    
+    # TODO: It would be better if we had unit tests for each
+    # method in addition to the following end-to-end test
+    def test_end_to_end(self):
+        print('Test: Empty stack')
+        stack = Stack()
+        assert_equal(stack.peek(), None)
+        assert_equal(stack.pop(), None)
+
+        print('Test: One element')
+        top = Node(5)
+        stack = Stack(top)
+        assert_equal(stack.pop(), 5)
+        assert_equal(stack.peek(), None)
+
+        print('Test: More than one element')
+        stack = Stack()
+        stack.push(1)
+        stack.push(2)
+        stack.push(3)
+        assert_equal(stack.pop(), 3)
+        assert_equal(stack.peek(), 2)
+        assert_equal(stack.pop(), 2)
+        assert_equal(stack.peek(), 1)
+        assert_equal(stack.is_empty(), False)
+        assert_equal(stack.pop(), 1)
+        assert_equal(stack.peek(), None)
+        assert_equal(stack.is_empty(), True)
+        
+        print('Success: test_end_to_end')
+
+def main():
+    test = TestStack()
+    test.test_end_to_end()
+    
+if __name__ == '__main__':
+    main()