      "class TestStackMin(object):\n",
      "\n",
      "    def test_stack_min(self):\n",
      "        print('Test: Push on empty stack, non-empty stack')\n",
      "        stack = MyStack()\n",
      "        stack.push(5)\n",
      "        assert_equal(stack.peek(), 5)\n",
      "        assert_equal(stack.min(), 5)\n",
      "        stack.push(1)\n",
      "        assert_equal(stack.peek(), 1)\n",
 
</s> remove     "        stack = MyStack()\n",
 </s> add     "        stack = StackMin()\n", </s> remove         stack = MyStack()
 </s> add         stack = StackMin() </s> remove     "        super(MyStack, self).__init__(top)\n",
 </s> add  </s> remove     "class MyStack(Stack):\n",
 </s> add     "class StackMin(Stack):\n", </s> remove     "        super(MyStack, self).push(data)\n",
 </s> add     "        super(StackMin, self).push(data)\n",
    "        stack = StackMin()\n",
      "class TestStackMin(object):\n",
      "\n",
      "    def test_stack_min(self):\n",
      "        print('Test: Push on empty stack, non-empty stack')\n",
    "        stack = StackMin()\n",
      "        stack.push(5)\n",
      "        assert_equal(stack.peek(), 5)\n",
      "        assert_equal(stack.min(), 5)\n",
      "        stack.push(1)\n",
      "        assert_equal(stack.peek(), 1)\n",
keep keep keep keep replace keep keep keep keep keep
 Polish stack min challenge and solution (#72)

Update constraints, algorithm discussion, code, and tests. 
stacks_queues/stack_min/stack_min_challenge.ipynb