Get cozy with echo - the Swiss Army knife for output in Fish.
echo
In Fish, the interactive shell is the default mode when you start it up.
Fish doesn’t have a built-in debugger like some other shells, but you can use external tools like gdb for debugging compiled programs or fish -d for running fish with debug output at different levels.
gdb
fish -d
Fish doesn’t have a built-in testing framework like some other programming environments.