[rspec-users] testing instance variables that are set inside views

Don Petersen don at donpetersen.net
Wed Jul 4 07:52:25 EDT 2007

I can sympathize with not wanting to just verify the final html  
output, even though it would probably be sufficient in this simple case.

I'm a big fan of helpers for any logic in views, even simple stuff  
like this.  If you had a couple of methods in your ApplicationHelper  
that handled setting and getting the page title value, that would be  
very easy to test.

Approaching it this way, you can use the helper specs to verify that  
the actual set/get logic worked.  You can even take that whole 'title  
= @header || "Default Title"' logic out of your layout if you wanted,  
and put it in the helper where you're only testing that logic and  
nothing more.

So in your view spec, where you had previously been wanting to test  
if an instance variable had been set, now you just need to verify  
that the helper method was called.  Like so:

That's how I have done this very logic in the past, and it feels  
right to me.

Alternately, if you don't want to use helpers, you might use  
CaptureHelper.html).  It's probably overkill for just a basic string  
like this, but maybe you can rig it to work in this case.


On Jul 4, 2007, at 11:09 AM, Patrick Ritchie wrote:

> David Chelimsky wrote:
>> On 7/4/07, Patrick Ritchie <pritchie at videotron.ca> wrote:
>>> aslak hellesoy wrote: On 7/3/07, Patrick Ritchie  
>>> <pritchie at videotron.ca> wrote: Hi, I think @header may not be an  
>>> implementation detail in this case. If your layout looks like  
>>> this: ... ... And the view we are testing looks like this: ... <% 
>>> = @header = 'Specific Title'> ... Then setting @header is an  
>>> essential behavior for the view spec. Or am I missing something?  
>>> Before I can answer about how to test this with RSpec, I need to  
>>> understand what's going on in the code. Isn't the head part of  
>>> the layout evaluated before the body? If that's the case, what's  
>>> the point of assigning the @header variable in the view? It  
>>> wouldn't change the title anyway The layout is evaluated after  
>>> the view so the above code is a useful way to include some piece  
>>> of data in the head without having to initialize it in the  
>>> controller. Very handy for things like head/title or view  
>>> specific onload js etc...
>> Correct me if I'm wrong, but it seems to me that the behavior  
>> you're interested in is that the right thing shows up in the  
>> title: response.should have_tag('title', 'whatever I am  
>> expecting') Am I missing something?
> I could do that, but that's not the really behavior I'm interested  
> in for the view. I'd rather look at the title tag in my layout spec  
> and the instance variable in my view.
> It doesn't really make a difference in this simple case, but it  
> would if the title was inserted from a partial called from the  
> layout, or the instance variable was used in multiple places in the  
> layout.
> Cheers!
> Patrick
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