diff --git a/Development-Testing.md b/Development-Testing.md
index f7b1579..02dedbb 100644
--- a/Development-Testing.md
+++ b/Development-Testing.md
@@ -27,6 +27,7 @@ flake8
 
 ### Complete test suite
 
+Note: in case of strange errors add option `-r` for recreation of environment
 ```
 tox
 ```