rspec users - Nov 2008 - rspec ''mock'' method not found

Hi,

I''m having trouble with "mock" and I can''t seem to
find any reason for
this.  The error...
********************
1)
NoMethodError in ''UserObserver should not call 
UserMailer.deliver_activation if user wasn''t recently
activated''
undefined method `mock'' for 
Spec::Rails::Example::ModelExampleGroup::Subclass_3:Class
./spec/models/user_observer_spec.rb:6:
/var/lib/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:177:in
`call''
/var/lib/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:177:in
`evaluate_method''
/var/lib/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:161:in
`call''
/var/lib/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:90:in
`run''
/var/lib/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:90:in
`each''
/var/lib/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:90:in
`send''
/var/lib/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:90:in
`run''
/var/lib/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:272:in
`run_callbacks''
spec/models/user_mailer_spec.rb:42:
********************

And the code....
********************
require File.dirname(__FILE__) + ''/../spec_helper''

context "A UserObserver" do
  setup do
    @user = mock(User)
    @user_observer = UserObserver.instance
  end

....<snip>....
end
********************

I''ve not found any other people with a similar issue via Google yet.

Any help is much appreciated.

-- 
Andy Koch