Add two test cases for editSub

basic edit and unset EDITOR

test.py

@@ -71,5 +71,30 @@ class TestAdd(unittest.TestCase):
         fileExists = os.path.isfile(os.path.join(os.getenv("TODO_DIR"), out[0], out[1]))
         self.assertTrue(fileExists)
 
+class TestEdit(unittest.TestCase):
+    def test_edit(self):
+        from unittest.mock import MagicMock
+        import subprocess
+
+        subprocess.call = MagicMock()
+        setup_environment("test1")
+        os.environ["EDITOR"] = "test"
+
+        sub.editSub(1)
+        subName = sub.getSub(sub.getItem(1))
+        subprocess.call.assert_called_with(["test", os.path.join(TEST_DATA_DIR, "test1", subName[0], subName[1])])
+
+    def test_edit_EDITOR_unset(self):
+        from unittest.mock import MagicMock
+        import subprocess
+
+        subprocess.call = MagicMock()
+        setup_environment("test1")
+        os.environ["EDITOR"] = ""
+
+        subName = sub.getSub(sub.getItem(1))
+        with self.assertRaises(SystemExit):
+            sub.editSub(1)
+
 if __name__ == '__main__':
     unittest.main()