In Rails 3's "rails runner", how do you use number_to_human_size() method?

Question

In a rails console, it can be done this way:

ree-1.8.7-2010.02 > helper.number_to_human_size 1
 => "1 Byte" 
ree-1.8.7-2010.02 > helper.number_to_human_size 100000
 => "97.7 KB" 
ree-1.8.7-2010.02 > helper.number_to_human_size 0
 => "0 Bytes" 
ree-1.8.7-2010.02 > helper.number_to_human_size 100000000
 => "95.4 MB" 

but what about in a rails runner? Is it running as a Controller? When I print out self.class it merely says Object