          sorted_data = merge_sort(data)
          assert_equal(sorted_data, [])
  
          print('One element')
          data = [5]
          sorted_data = merge_sort(data)
          assert_equal(sorted_data, [5])
  
          print('Two or more elements')
          data = [5, 1, 7, 2, 6, -3, 5, 7, -1]
          sorted_data = merge_sort(data)
          assert_equal(sorted_data, sorted(data))
 
</s> remove         sorted_data = merge_sort(data)
        assert_equal(sorted_data, sorted(data))
 </s> add         assert_equal(merge_sort.sort(data), sorted(data)) </s> remove         data = []
        sorted_data = merge_sort(data)
        assert_equal(sorted_data, [])
 </s> add         assert_equal(merge_sort.sort([]), []) </s> remove     "        data = [5]\n",
    "        sorted_data = merge_sort(data)\n",
    "        assert_equal(sorted_data, [5])\n",
 </s> add     "        assert_equal(merge_sort.sort([5]), [5])\n", </s> remove     "        data = [5]\n",
    "        sorted_data = merge_sort(data)\n",
    "        assert_equal(sorted_data, [5])\n",
 </s> add     "        assert_equal(merge_sort.sort([5]), [5])\n", </s> remove     "        sorted_data = merge_sort(data)\n",
    "        assert_equal(sorted_data, sorted(data))\n",
 </s> add     "        assert_equal(merge_sort.sort(data), sorted(data))\n",
        assert_equal(merge_sort.sort([5]), [5])
          sorted_data = merge_sort(data)
          assert_equal(sorted_data, [])
  
          print('One element')
        assert_equal(merge_sort.sort([5]), [5])
        assert_equal(merge_sort.sort([5]), [5])
        assert_equal(merge_sort.sort([5]), [5])
  
          print('Two or more elements')
          data = [5, 1, 7, 2, 6, -3, 5, 7, -1]
          sorted_data = merge_sort(data)
          assert_equal(sorted_data, sorted(data))
keep keep keep keep replace replace replace keep keep keep keep keep
 Update merge sort challenge (#130)

Update constraints, test cases, code, and tests. 
sorting_searching/merge_sort/test_merge_sort.py