      "# %load test_min_heap.py\n",
      "from nose.tools import assert_equal\n",
      "\n",
      "\n",
      "class TestMinHeap(object):\n",
      "\n",
      "    def test_min_heap(self):\n",
      "        heap = MinHeap()\n",
      "        assert_equal(heap.peek_min(), None)\n",
      "        assert_equal(heap.extract_min(), None)\n",
 
</s> remove     "class TestMinHeap(object):\n",
 </s> add     "class TestMinHeap(unittest.TestCase):\n", </s> remove     "        assert_equal(heap.peek_min(), None)\n",
    "        assert_equal(heap.extract_min(), None)\n",
 </s> add     "        self.assertEqual(heap.peek_min(), None)\n",
    "        self.assertEqual(heap.extract_min(), None)\n", </s> remove     "        assert_equal(heap.peek_min(), None)\n",
    "        assert_equal(heap.extract_min(), None)\n",
 </s> add     "        self.assertEqual(heap.peek_min(), None)\n",
    "        self.assertEqual(heap.extract_min(), None)\n", </s> remove     "from nose.tools import assert_equal\n",
 </s> add     "import unittest\n", </s> remove     "        assert_equal(heap.peek_min(), 20)\n",
 </s> add     "        self.assertEqual(heap.peek_min(), 20)\n",
    "class TestMinHeap(unittest.TestCase):\n",
      "# %load test_min_heap.py\n",
      "from nose.tools import assert_equal\n",
      "\n",
      "\n",
    "class TestMinHeap(unittest.TestCase):\n",
      "\n",
      "    def test_min_heap(self):\n",
      "        heap = MinHeap()\n",
      "        assert_equal(heap.peek_min(), None)\n",
      "        assert_equal(heap.extract_min(), None)\n",
keep keep keep keep replace keep keep keep keep keep
 #273: Remove nose dependency for graphs_trees/ (#277) 
graphs_trees/min_heap/min_heap_challenge.ipynb