Question about slug generation

[terenceponce]

I'm trying to improve some of the model tests by using shoulda-matchers and I came across something interesting about slug generation.

I tried changing this part:

describe 'with blank title' do
  before { @article.title = ' ' }
  it { should_not be_valid }
end

into this:

it { should validate_presence_of(:title) }

and I got this error:

Failure/Error: it { should validate_presence_of(:title) }
NoMethodError:
undefined method to_slug for nil:NilClass
# ./app/models/article.rb:40:in generate_slug
# ./spec/models/article_spec.rb:39:in block (2 levels) in <top (required)>

The shoulda-matcher, validate_presence_of is passing nil to test presence validation, but it turns out, slug generation happens before validation and the error is happening because :title is nil. Does generate_slug really have to happen before validation or can we put it in another callback?

[bryanbibat]

The only reason generate_slug is done before validation is so that a slug can be generated on create and update (e.g. the user deleted the slug on update for it to re-generate a new one).

Feel free to add nil checking or some other approach as long as this behavior (generating slug on create and update) is implemented.