Rails - Aug 2005 - Controllers have no session object when you construct them, so how can I test the flash?

Hi folks,

I''m attempting to _unit_ test a controller. This may sound a little 
wacky to those who only perform functional tests on controllers, but I 
find that it''s much easier to do, runs much faster, and better suits my
XP style development methodology. Also (and very importantly in my 
case), it seems to be just about the only way to test controllers used 
in components.

Anyway, it''s been going very well, until suddenly I want to use the
flash.

Because I constructed my own controller, it appears to have no session 
object, and thus call to it''s "flash" method ends up indexing
null.

For example, consider the controller. And test below.

--------------------------------------------------------------------
class Blog::ComponentController < ActionController::Base
    def edit
        flash[''notice''] = ''performing edit
action''
    end
end

class BlogControllerTest < Test::Unit::TestCase
    def test_edit_does_something
        controller = Blog::ComponentController.new
        controller.edit
    end
end
--------------------------------------------------------------------

In this case, test_edit_does_something will call controller.edit, which 
will cause it an exception when it tries to use the flash. In controller 
functional tests I would normally call "get" or "post" in
order the
power up the whole rails framework and get it to use the controller. 
I''ve spent a couple of hours pouring through that code, and I
can''t
figure out how the controller''s session get''s initialised
during that
process, or what I can do myself to fake it.

Any ideas would be much appreciated.

Craig

Hi folks,

I''m attempting to _unit_ test a controller. This may sound a little
wacky to those who only perform functional tests on controllers, but I
find that it''s much easier to do, runs much faster, and better suits my
XP style development methodology. Also (and very importantly in my
case), it seems to be just about the only way to test controllers used
in components.

Anyway, it''s been going very well, until suddenly I want to use the
flash.

Because I constructed my own controller, it appears to have no session
object, and thus call to it''s "flash" method ends up indexing
null.

For example, consider the controller. And test below.

--------------------------------------------------------------------
class Blog::ComponentController < ActionController::Base
    def edit
        flash[''notice''] = ''performing edit
action''
    end
end

class BlogControllerTest < Test::Unit::TestCase
    def test_edit_does_something
        controller = Blog::ComponentController.new
        controller.edit
    end
end
--------------------------------------------------------------------

In this case, test_edit_does_something will call controller.edit, which
will cause it an exception when it tries to use the flash. In controller
functional tests I would normally call "get" or "post" in
order the
power up the whole rails framework and get it to use the controller.
I''ve spent a couple of hours pouring through that code, and I
can''t
figure out how the controller''s session get''s initialised
during that
process, or what I can do myself to fake it.

Any ideas would be much appreciated.

Craig

On Aug 29, 2005, at 6:01 PM, Craig Ambrose wrote:
> Because I constructed my own controller, it appears to have no  
> session object, and thus call to it''s "flash" method
ends up
> indexing null.
> ...
> In this case, test_edit_does_something will call controller.edit,  
> which will cause it an exception when it tries to use the flash. In  
> controller functional tests I would normally call "get" or
"post"
> in order the power up the whole rails framework and get it to use  
> the controller. I''ve spent a couple of hours pouring through that
> code, and I can''t figure out how the controller''s session
get''s
> initialised during that process, or what I can do myself to fake it.
>
> Any ideas would be much appreciated.
I look forward to hearing  other responses to this...

I have been working with Sails, which has the same challenge. When I  
began months ago, I wanted to test Controllers just as you described:  
invoke the action directly. Sails has everything needed to mock the  
HttpServletRequest and HttpServletResponse, so it seemed the natural  
thing to do. It quickly became a nightmare to maintain.

Think about your action: it has an instance variable for a request,  
which I would suppose is coming from ActionController::Base or being  
added at some other point. By the time your action is invoked, it''s  
all there. If you unit test as you describe, something needs to set  
all that up. What I did in Sails, at first, was create a  
ControllerTestCase that could be sub-classed: it provided a  
''createController'' method. This had to effectively duplicate
whatever
was happening in the framework to create an instance of a Controller  
and initialize it''s context. This became especially burdensome to the  
developer when the Controller had dependencies, which are being met  
through Inversion of Control. How could they easily inject mocks?  
More challenging: how could they NOT inject mocks - use the  
components defined for application runtime because they are the best  
choice - without have to go back to every test class when you add new  
components, or, worse, duplicate something?

Anyway, I ended up doing what Rails does. Execute as much of the real  
code as possible, replacing key pieces with fakes that make testing  
easier. Its feeling more and more like Rails ''functional''
tests.

Looking back, I think my desire to do the testing ''unit'' style
was
well motivated. In reality, it provided very little value. That said,  
if there is a good way...

Hopefully Helpful,

  adam williams