test_fun: Tests a function by checking if its arguments are declared
Description
This function verifies whether all of the arguments of another
function already have assigned values. If an argument has a default value
but there isn't a corresponding variable, it creates that variable.
Usage
test_fun(f, force_default = FALSE)
Arguments
f
A function
force_default
Whether or not to assign the default value to arguments
that already have assigned values