Why is my format validation failing for permalinks?

Why is my format validation failing for permalinks?

I have written an rspec test for checking invalid characters in my permalink:
describe "formatting permalinks when creating a page" do
it "does not allow crazy characters" do
page = create(:page, permalink: '#$%^&*first-title')
expect(page).to have(1).errors_on(:permalink)
end
end
In my page.rb model, I have this validation implemented to make it pass:
class Page < ActiveRecord::Base
validates :permalink, format: {:with => /\A[a-zA-Z-]+\Z/, :on => :save!}
before_create :create_slug
def create_slug
self.permalink = self.permalink.parameterize
end
end
But I get his error:
expected 1 errors on :permalink, got 0
What am I doing wrong? How do I fix this?