add docstring.

Author: aymanelsayeed

tests/conftest.py

@@ -1,11 +1,26 @@
+"""
+
+This file contains fixtures that are used in the test cases.
+
+"""
 from pytest import fixture
 
 
 @fixture(scope="session", params=[(2, 1, 1), (3, 2, 1)])
 def data_to_add(request):
+    """
+    Fixture for add function
+    :param request: request object
+    :return: tuple of parameters for add function
+    """
     yield request.param
 
 
 @fixture(scope="session", params=[(2, 3, 1), (3, 4, 1)])
 def data_to_sub(request):
+    """
+    Fixture for sub function
+    :param request: request object
+    :return: tuple of parameters for sub function
+    """
     yield request.param