Small fix

Author: astyagun

README.md

@@ -989,7 +989,7 @@ they will retry the match for given timeout allowing you to test ajax actions.
     article = mock_model(Article).as_null_object
     ```
 
-* Use `let` blocks instead of `before(:all)` blocks to create data for
+* Use `let` blocks instead of `before(:each)` blocks to create data for
   the spec examples. `let` blocks get lazily evaluated.
 
     ```Ruby