Add sum two challenge

online_judges/sum_two/test_sum_two.py

@@ -0,0 +1,21 @@
+from nose.tools import assert_equal, assert_raises
+
+
+class TestSumTwo(object):
+
+    def test_sum_two(self):
+        solution = Solution()
+        assert_raises(TypeError, solution.sum_two, None)
+        assert_equal(solution.sum_two(5, 7), 12)
+        assert_equal(solution.sum_two(-5, -7), -12)
+        assert_equal(solution.sum_two(5, -7), -2)
+        print('Success: test_sum_two')
+
+
+def main():
+    test = TestSumTwo()
+    test.test_sum_two()
+
+
+if __name__ == '__main__':
+    main()