module ThoughtBot::Shoulda::Controller::Macros

def should_assign_to(*names)

should_assign_to :user, :equals => '@user'
should_assign_to :user, :class => User
should_assign_to :user, :posts

Example:

the instance variable being checked.
* :equals - A string which is evaluated and compared for equality with
* :class - The expected class of the instance variable being checked.
Options:

each of the named instance variable(s).
Macro that creates a test asserting that the controller assigned to 
def should_assign_to(*names)
  opts = names.extract_options!
  names.each do |name|
    test_name = "assign @#{name}"
    test_name << " as class #{opts[:class]}" if opts[:class]
    test_name << " which is equal to #{opts[:equals]}" if opts[:equals]
    should test_name do
      assigned_value = assigns(name.to_sym)
      assert assigned_value, "The action isn't assigning to @#{name}"
      assert_kind_of opts[:class], assigned_value if opts[:class]
      if opts[:equals]
        instantiate_variables_from_assigns do
          expected_value = eval(opts[:equals], self.send(:binding), __FILE__, __LINE__)
          assert_equal expected_value, assigned_value,
                       "Instance variable @#{name} expected to be #{expected_value}" + 
                       " but was #{assigned_value}"
        end
      end
    end
  end
end