rspec users - May 2010 - questions about meta-programming in a shared_examples group

I''ve created a shared_examples group that helps me dry up the testing
of a large set of similar rails controllers.

These controllers have an html interface but mostly what I am testing with the
shared_examples group is the rendering of four
different forms of xml that relate to running a dynamically created Java Web
Start jnlp.

The html reports when running one of the controller specs looks like this:

   Embeddable::DataCollectorsController GET show with mime type of otml
   renders the requested data_collector as otml without error

Here''s an example of what one of the controller specs looks like:

http://github.com/stepheneb/rigse/blob/master/spec/controllers/embeddable/data_collectors_controller_spec.rb

   require ''spec_helper''

   describe Embeddable::DataCollectorsController do

     it_should_behave_like ''an embeddable controller''

     def with_tags_like_an_otml_data_collector
       with_tag(''OTDataCollector'') do
         with_tag(''source'') do
           with_tag(''OTDataGraphable'') do
             with_tag(''dataProducer'')
           end
         end
         with_tag(''xDataAxis'') do
           with_tag(''OTDataAxis'')
         end
         with_tag(''yDataAxis'') do
           with_tag(''OTDataAxis'')
         end
       end
     end

   end

I love how clearly each controller spec reads now and how the part that is
different in the otml rendering stands out.

But I wondered if the way I am using lambdas in the shared_examples helper is
fragile and might break if internals in rspec
change. The meta-programming I did to get some of this to work seemed a bit
messy and I was wondering if there was a simpler
way.

The describe statement in the shared_examples_for ''an embeddable
controller'' for that example looks like this:

   describe "with mime type of otml" do
     it "renders the requested #{model_ivar_name_lambda.call} as otml
without error" do

The beginning of the shared_examples group looks like this:

  
http://github.com/stepheneb/rigse/blob/master/spec/support/embeddable_controller_helper.rb

   shared_examples_for ''an embeddable controller'' do
     integrate_views

     controller_class_lambda = lambda {
       self.send(:described_class)
     }
     model_class_lambda      = lambda {
       controller_class_lambda.call.name[/(.*)Controller/,
1].singularize.constantize
     }
     model_ivar_name_lambda  = lambda {
       model_class_lambda.call.name.delete_module.underscore_module
     }

     def with_tags_like_an_otml(model_name)
       self.send("with_tags_like_an_otml_#{model_name}".to_sym)
     end

     before(:each) do
       @model_class = model_class_lambda.call
       @model_ivar_name = model_ivar_name_lambda.call
       unless
instance_variable_defined?("@#{@model_ivar_name}".to_sym)
         @model_ivar = instance_variable_set("@#{@model_ivar_name}",
           Factory.create(@model_ivar_name))
       end
     end


The method in the controller spec: with_tags_like_an_otml_data_collector is used
in the shared_examples group later like this:

   with_tag(''library'') do
     with_tags_like_an_otml(@model_ivar_name)
   end

Hi Stephen,

On May 10, 2010, at 8:48 PM, Stephen Bannasch wrote:
> I''ve created a shared_examples group that helps me dry up the
testing of a large set of similar rails controllers.
> 
> These controllers have an html interface but mostly what I am testing with
the shared_examples group is the rendering of four different forms of xml that
relate to running a dynamically created Java Web Start jnlp.
> 
> The html reports when running one of the controller specs looks like this:
> 
>  Embeddable::DataCollectorsController GET show with mime type of otml
>  renders the requested data_collector as otml without error
> 
> Here''s an example of what one of the controller specs looks like:
> 
>
http://github.com/stepheneb/rigse/blob/master/spec/controllers/embeddable/data_collectors_controller_spec.rb
> 
>  require ''spec_helper''
> 
>  describe Embeddable::DataCollectorsController do
> 
>    it_should_behave_like ''an embeddable controller''
> 
>    def with_tags_like_an_otml_data_collector
>      with_tag(''OTDataCollector'') do
>        with_tag(''source'') do
>          with_tag(''OTDataGraphable'') do
>            with_tag(''dataProducer'')
>          end
>        end
>        with_tag(''xDataAxis'') do
>          with_tag(''OTDataAxis'')
>        end
>        with_tag(''yDataAxis'') do
>          with_tag(''OTDataAxis'')
>        end
>      end
>    end
> 
>  end
> 
> I love how clearly each controller spec reads now and how the part that is
different in the otml rendering stands out.
> 
> But I wondered if the way I am using lambdas in the shared_examples helper
is fragile and might break if internals in rspec change. The meta-programming I
did to get some of this to work seemed a bit messy and I was wondering if there
was a simpler way.
The most obvious problem is that "have_tag" and "with_tag"
will not be supported in rspec-rails-2.

I haven''t looked at it in a while, but you may want to take a look at
the assert2 gem. It''s mostly focused on test/unit assertions, but there
is an rspec matcher named be_html_with that offers a nice dsl for something
close to what you''re trying to do. Check the bottom of
http://groups.google.com/group/merb/browse_thread/thread/3588d3f75fa0e65c.
> The describe statement in the shared_examples_for ''an embeddable
controller'' for that example looks like this:
> 
>  describe "with mime type of otml" do
>    it "renders the requested #{model_ivar_name_lambda.call} as otml
without error" do
> 
> The beginning of the shared_examples group looks like this:
> 
> 
http://github.com/stepheneb/rigse/blob/master/spec/support/embeddable_controller_helper.rb
> 
>  shared_examples_for ''an embeddable controller'' do
>    integrate_views
> 
>    controller_class_lambda = lambda {
>      self.send(:described_class)
>    }
>    model_class_lambda      = lambda {
>      controller_class_lambda.call.name[/(.*)Controller/,
1].singularize.constantize
>    }
>    model_ivar_name_lambda  = lambda {
>      model_class_lambda.call.name.delete_module.underscore_module
>    }
> 
>    def with_tags_like_an_otml(model_name)
>      self.send("with_tags_like_an_otml_#{model_name}".to_sym)
>    end
> 
>    before(:each) do
>      @model_class = model_class_lambda.call
>      @model_ivar_name = model_ivar_name_lambda.call
>      unless
instance_variable_defined?("@#{@model_ivar_name}".to_sym)
>        @model_ivar =
instance_variable_set("@#{@model_ivar_name}",
>          Factory.create(@model_ivar_name))
>      end
>    end
> 
> 
> The method in the controller spec: with_tags_like_an_otml_data_collector is
used in the shared_examples group later like this:
> 
>  with_tag(''library'') do
>    with_tags_like_an_otml(@model_ivar_name)
>  end
> 
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