Rails core - Feb 2006 - #3775 - testing helpers which use ActionView methods

http://dev.rubyonrails.org/ticket/3775  

I''m hoping someone will pop up and tell me I''m simply daft
with this
ticket (and queries on IRC, and a prior post to the main Rails list),
but I can''t get a peep out of anyone so far.

The question is, how do I write a simple test for a helper method which
calls ActionView methods itself.  E.g., a foo_link() helper which calls
link_to().  I noticed that Typo doesn''t test these, though it seems to
have tests for everything else.

Am I missing something, or is there a gap here in Rails'' testability?

Best,
Rick
-- 
 http://www.rickbradley.com    MUPRN: 485
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On 2/9/06, Rick Bradley <rick@rickbradley.com>
wrote:
>
>      http://dev.rubyonrails.org/ticket/3775
>
> I''m hoping someone will pop up and tell me I''m simply
daft with this
> ticket (and queries on IRC, and a prior post to the main Rails list),
> but I can''t get a peep out of anyone so far.
>
> The question is, how do I write a simple test for a helper method which
> calls ActionView methods itself.  E.g., a foo_link() helper which calls
> link_to().  I noticed that Typo doesn''t test these, though it
seems to
> have tests for everything else.
>
> Am I missing something, or is there a gap here in Rails''
testability?
>
> Best,
> Rick
Check out the ActionView tests.  Here''s the tag helper tests, for
example:

http://dev.rubyonrails.org/browser/trunk/actionpack/test/template/tag_helper_test.rb

The url_for tests require a controller, so you''ll see some of them
creating fake controllers with the bare minimum defined.

--
Rick Olson
http://techno-weenie.net

* Rick Olson (technoweenie@gmail.com) [060209 16:15]:
> Check out the ActionView tests.  Here''s the tag helper tests, for
example:
> 
>
http://dev.rubyonrails.org/browser/trunk/actionpack/test/template/tag_helper_test.rb
> 
> The url_for tests require a controller, so you''ll see some of them
> creating fake controllers with the bare minimum defined.
Rick,
Thanks for the assistance!

I guess my question is more about how one has to go about testing these
sorts of helpers -- maybe it''s more a question of philosophy than
feasability.  

For example, in our case, we had a developer trying to write a
functional test for a helper which called link_to().  He ended up in the
weeds and I started working with him and quickly came to the realization
that we had two options (we were indeed declaring a bare-minimum
controller for the test, as #3775 showed):

 (1) Stub the link_to() method so that the dependency problem ceases to
 exist.

 (2) Each time we get an error for a method that can''t be found, track
 down the method in the Rails framework and add a require/include to
 make it visible.

While (2) is a reasonable method to test helpers that are written inside
Rails itself (since they are expected to have some knowledge of the
layout of the framework), it''s a bad Code Smell for tests of helpers in
application code.  

Not only does this technique require ferreting out the location of
dependent methods from the Rails class hierarchy, but it forces the
tester to do white box testing on the helper method in the first place.
The tester has to know that the helper is relying upon certain specific
Rails calls to get its job done, and then has to load those specific
pieces to get his test written.  

If the internal helper code changes, the require/include list in the
test may well get out of date (more bad smell).

If the layout of Rails changes in the future, tests will break because
they will fall out of sync with the layout of whichever Rails modules
the dependent methods needed in place.

Anyway, when Rails is running and a helper is called the call succeeds
and the developer never had to go around trying to pick out which Rails
modules have to be included to make that helper run.  Why should testing
that helper suddenly require the developer to become familiar with the
layout of the Rails guts?  Another way:  the helper tests are too damned
coupled to the Rails guts.

Granted, there''s probably more important things to worry about, but if
I
wanted to write a bunch of library inclusion lines for a snippet of code
I''d go back to Java.  Seems like there should be a Railsy way to just
write the obvious black-box test and not have to fight the framework to
get it done.

Thanks,
Rick
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