diff --git a/README.md b/README.md
index f10edc125..f6df9fdcf 100644
--- a/README.md
+++ b/README.md
@@ -385,6 +385,7 @@ To improve the GNU compatibility, the following process is recommended:
 1. Start to modify `<your test>` to understand what is wrong. Examples:
     1. Add `set -v` to have the bash verbose mode
     1. Add `echo $?` where needed
+    1. When the variable `fail` is used in the test, `echo $fail` to see when the test started to fail
     1. Bump the content of the output (ex: `cat err`)
     1. ...
 1. Or, if the test is simple, extract the relevant information to create a new test case running both GNU & Rust implementation