diff --git a/gradefetcher/gradefetcher.py b/gradefetcher/gradefetcher.py
index e31ab68..e4aeb39 100644
--- a/gradefetcher/gradefetcher.py
+++ b/gradefetcher/gradefetcher.py
@@ -1,6 +1,7 @@
 import logging
 import os
 import urllib.parse
+from operator import truediv
 
 import pkg_resources
 import requests
@@ -20,6 +21,16 @@
 loader = ResourceLoader(__name__)
 
 
+def grade_from_list(grades):
+    """take a list of integers and calculate grade from them"""
+    if len(grades) > 1:
+        total_grade = sum(grades)
+        grade = int(truediv(total_grade * 100, len(grades)))
+    else:
+        grade = grades[0] * 100
+    return grade
+
+
 @XBlock.needs("i18n", "user")
 @XBlock.wants("settings")
 class GradeFetcherXBlock(XBlock, StudioEditableXBlockMixin):
@@ -399,15 +410,7 @@ def grade_user(self, data, suffix=""):
                     for result in grader_response.json()["results"]:
                         if "grade" in result:
                             grades.append(result["grade"])
-                    if len(grades) > 1:
-                        from operator import truediv
-
-                        total_grade = 0
-                        for g in grades:
-                            total_grade += g
-                        grade = int(truediv(total_grade * 100, len(grades)))
-                    else:
-                        grade = grades[0] * 100
+                    grade = grade_from_list(grades)
                     reasons = []
                     for result in grader_response.json()["results"]:
                         if "grade" in result:
diff --git a/gradefetcher/tests/test_gradefetcher.py b/gradefetcher/tests/test_gradefetcher.py
new file mode 100644
index 0000000..3534dac
--- /dev/null
+++ b/gradefetcher/tests/test_gradefetcher.py
@@ -0,0 +1,13 @@
+import unittest
+
+from gradefetcher.gradefetcher import grade_from_list
+
+
+class GradeFetcherHelperTests(unittest.TestCase):
+    def test_grade_from_list(self):
+        assert grade_from_list([0]) == 0
+        assert grade_from_list([1]) == 100
+        assert grade_from_list([2]) == 200
+        assert grade_from_list([0, 0]) == 0
+        assert grade_from_list([1, 1]) == 100
+        assert grade_from_list([1, 0]) == 50