diff --git a/mb/tests/conf_tests.py b/mb/tests/conf_tests.py
new file mode 100644
index 00000000..618b7774
--- /dev/null
+++ b/mb/tests/conf_tests.py
@@ -0,0 +1,22 @@
+import unittest
+
+from mb.conf import adjust_zsync_block_size_for_1G
+
+
+class TestConfig(unittest.TestCase):
+
+    def test_adjust_zsync_block_size_for_1G(self):
+        cases = {
+            0: None,
+            1023: None,
+            1025: 1024,
+            3*1024: 2*1024,
+            4*1024: 4*1024,
+            4*1024+1: 4*1024,
+            1024*1024*1024+1: 1024*1024*1024
+        }
+        for n in cases:
+            self.assertEqual(cases[n], adjust_zsync_block_size_for_1G(n), "for input " + repr(n))
+
+if __name__ == '__main__':
+    unittest.main()