fix cli bug + add cli tests

tests/test_cli.py

@@ -40,4 +40,6 @@ _test_cli(
         "--pretty",
     ],
 )
-_test_cli(collection_diff, ["--remote_id", "spot-6-7-drs", "--col_path", "/tmp/col.json"])
+_test_cli(
+    collection_diff, ["--remote_id", "spot-6-7-drs", "--col_path", "/tmp/col.json"]
+)