mandatory

# Prints without a new line
echo -n hello

# update env variable value
export HELLO=123
export HELLO="beautiful world"

# keep track of OLDPWD
cd obj
echo $PWD $OLDPWD

# invalid command, followed by empty input, should keep the exit code
doesntexist

echo $?

#invalid command, followed by empty variable, should clear the exit code
doesntexist
$EMPTY
echo $?

# Check if there isn't a zombie process called `cat`
echo "hi" | cat | cat | cat | cat | cat | cat | cat
ps -a

# Should skip the empty argument, and print hello after spaces
echo - "" "  " hello

# Neither of these unsets should break the shell, and you should still be able to call `/bin/ls`
unset USER
unset PATH
unset PWD
/bin/ls

# This should not change the current directory
cd .. hi

# Empty `cd` moves to home
cd