[rspec-users] A bit confused with the use of assign() to test views

[ct9a]

hi guys,
 I'm trying to pick up Rspec to port an existing application in rails
2.3.8 to rails 3.

I'm using the pragmatic "The Rspec book" (dec 2010) as a reference.
read around the book and the rspec docs.

1) assign method
    - syntax: assign( <symbol name>, <block usually calling double()
or mock_model)>
    - what it means to me: run the codes in the block and assign the
value evaluated to the symbol name.


2) let method
syntax: let(method_name>)  { … }
- will not run until it is called
-used with before(), end() to set up usually instance variables
-the contents in its block will be evaluated when called
-here's what http://rdoc.info/gems/rspec/1.3.2/frames says when i
looked up the source for let.

------ Documentation extract for "let" (start) ----------------------
def let(name, &block)
  define_method name do
    @assignments ||= {}
    @assignments[name] ||= instance_eval(&block)
  end
end
------ Documentation extract for "let" (end) ----------------------

-to call the contents of the block, we will refer to it by the method
name (which is a symbol)


There's this example below (from the rspec book page  338) which I am
a little confused with.

------------ Extract start ----------------------------

  1 require 'spec_helper'
  2
  3 describe "messages/new.html.erb" do
  4   let(:message) do
  5     mock_model("Message").as_new_record.as_null_object
  6   end
  7
  8   before do
  9     assign(:message, message)
 10   end
 11
 12   it "renders a form to create a message" do
 13     render
 14     rendered.should have_selector("form",
 15       :method => "post",
 16       :action => messages_path
 17     ) do |form|
 18       form.should have_selector("input", :type => "submit")
 19     end
 20   end
 21
 22   it "renders a text field for the message title" do
 23     message.stub(:title => "the title")
 24     render
 25     rendered.should have_selector("form") do |form|
 26       form.should have_selector("input",
 27         :type => "text",
 28         :name => "message[title]",
 29         :value => "the title"
 30       )
 31     end
 32   end
 33 end
------------ Extract end   ----------------------------

My question is, line 9 seems to imply that the content of :message
(the mocked Message object) is being
assigned to the 'message' object but as per what I have read in the
Rspec book, the first argument in the call to assign() is actually the
variable that is getting assigned with.

Yet, the extract above still works when i run "rake spec".

I'm a bit confused.

Please help.


Thanks