rspec vs 'url_validation' gem - ruby-on-rails-3

Question

I'm struggling with rspec as a new Rails person and I have a need to validate a url passed into Active Record. This is probably due to my ignorance so pls point me in the right direction. The video_url is a string field which I'd like to validate as being a valid URL. Looking around, I chose this gem because it appeared to be fully tested in rspec. For my test I didn't see how I could incorporate his validation test into my model test.
In rails console, I created a Post object and ensured that if I put a bogus URL that I knew would not be found, I would get an error. The curious thing is that attempting to replicate this in a test with the gem installed fails the test because it finds no errors. I expected an error of some kind as I got in console. My question is what am I doing wrong in that it gets no errors? I've made several attempts to triangulate what might be causing it but the gem doesn't seem to work in rspec? I would have thought that if I could get it to work in console, I can get it to work in rspec?
post.rb
class Post < ActiveRecord::Base
attr_accessible :body, :title, :image, :video_title, :video_url
validates_presence_of :title, :body, :author
validates :video_url, :presence => true, :if => :video_title_present?, :url => {
:check_path => [ 300..399, 400..499, 500..599 ], :allow_nil => true,
:url_not_accessible_message => "must be valid.",
:invalid_url_message => "must be valid.",
:url_invalid_response_message => "must be valid."}
def video_title_present?
!self.video_title.blank?
end
belongs_to :author, class_name: "User"
end
post_spec.rb
before do
#post = Post.new(title: "foo", body: "my body here")
end
describe "validates with video links" do
it "validates with video url and video title" do
#post.video_url = "http://heckitoqi.com"
#post.video_title = "my title"
#post.should have_at_least(1).error_on(:video_url)
end
end
Output in console:
Failure/Error: #post.should have_at_least(1).error_on(:video_url)
expected at least 1 error on :video_url, got 0
In some of my errors, I attempted a more open-ended error, but it fails by not catching any errors.
Here is a short version of my smoke test of the model using Rails console:
u = User.first
p = Post.new(title: "title", body: "body", video_title: "vtitle", video_url: "http://heckitoqi.com")
p.author = u
p.save!
>> HTTPI GET request to heckitoqi.com (net_http)
>> ActiveRecord::RecordInvalid: Validation failed: Video url must be valid.
If I can get it to validate in the console, then my implementation of the test is at fault, right? I just don't see what I'm doing wrong. thanx, sam