          sorted_data = merge_sort(data)
          assert_equal(sorted_data, None)
  
          print('Empty input')
          data = []
          sorted_data = merge_sort(data)
          assert_equal(sorted_data, [])
  
          print('One element')
          data = [5]
          sorted_data = merge_sort(data)
          assert_equal(sorted_data, [5])
 
</s> remove         data = [5]
        sorted_data = merge_sort(data)
        assert_equal(sorted_data, [5])
 </s> add         assert_equal(merge_sort.sort([5]), [5]) </s> remove         data = None
        sorted_data = merge_sort(data)
        assert_equal(sorted_data, None)
 </s> add         assert_raises(TypeError, merge_sort.sort, None) </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 = []\n",
    "        sorted_data = merge_sort(data)\n",
    "        assert_equal(sorted_data, [])\n",
 </s> add     "        assert_equal(merge_sort.sort([]), [])\n",
        assert_equal(merge_sort.sort([]), [])
          sorted_data = merge_sort(data)
          assert_equal(sorted_data, None)
  
          print('Empty input')
        assert_equal(merge_sort.sort([]), [])
        assert_equal(merge_sort.sort([]), [])
        assert_equal(merge_sort.sort([]), [])
  
          print('One element')
          data = [5]
          sorted_data = merge_sort(data)
          assert_equal(sorted_data, [5])
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