notes: document behaviour we need to implement so that we can use prysk

NOTES.md

@@ -7,6 +7,15 @@ Comparative testing with bash should be done with bash --norc --posix.
 ## Ideas for testing
 * use prysk or shellspec with shell=./minishell
 
+### Prysk
+Seems like it would work, but only after we implement execution of simple commands, and the $? variable, since prysk (and cram as well) relie on it to collect the exit status.
+
+For it to work, the shell must be able to execute the following command:
+```shell
+$ echo PRYSK12345 2 $?
+PRYSK12345 2 0
+```
+
 ## Shell Operation
 
 cf. 3.1.1 Shell Operation