How can I "source" expect script

I'm forced to use a script like below:

# test.sh
function my_fun
{
    echo "Give value for FOO"
    local my_var
    read my_var
    export FOO=$my_var
}

# Call my_fun function
my_fun

by sourcing it from my shell.

$ source test.sh
Give value for FOO
stackexchange
$ echo $FOO
stackexchange

I would like to automate the script with expect like shown below:

$ expect test.exp
$ echo $FOO
stackexchange

The amount and names of the environmental variables in test.sh is unknown.

Update:

• Added my_fun functionc all to test.sh.