Whene i run this command :
>radiusd -x

in the end i have : Ready to process requests

it means that the server is running corrcetly and waiting for requests .

but i still don't know why the test doesnt work

this will show you why its failing. as said before, suspect
100% file permissions - either on eg /var/log/radiusd type files
or /var/run/radiusd/ directory etc

which permission shoud i give to these files and how can i do it ?

thank you for your help