Where do I put the -p flag when running a "rails generate" in "pretend" mode?

The Rails help message says:

General options:  -h, [--help]     # Print generator's options and usage  -p, [--pretend]  # Run but do not make any changes  -f, [--force]    # Overwrite files that already exist  -s, [--skip]     # Skip files that already exist  -q, [--quiet]    # Suppress status output

I'm specifically interested in -p to see what files would be generated. However, the following commands don't work:

rails generate -p migration CreateFoo foo:stringrails generate migration -p CreateFoo foo:string

How do I run a "pretend" generate command in Rails?