Answer by Sergey Ponomarev for CGI not working with httpd server on busybox 1.15.0 on ltib linux 2.6.34 (404 page not found)

You just have a wrong file name: you called it testcgi but calling cgitest.I'll recommended to rename it to test.cgi or even test.sh. If the cgi script is main e.g. like index.php then you can call it index.cgi and the you can just specify a directory without the /cgi-bin/index.cgi.

You can start the bb httpd in non-daemon mode with logging and you'll see errors:

busybox httpd -f -vv -p 8080

Here the -vv is a verbose mode and -f means "Don't daemonize" in keep in foreground.

Also please note the permission to a folder may be not ehough and you may need to specify a permission for the specific script