Is it possible to call truncate method in rspec feature test? - ruby-on-rails-3

Question

I'm using Rails 3.2, Rspec 2 and capybara 2.
I am truncating a string of body text in my webpage and would like to test this in my feature spec.
Can someone advise how to do this because I can't seem to call truncate in my test because it keeps saying it's an undefined method and I don't really want to have a long string of truncated text in my test suite; just applying the truncate function is good enough.
I've tried using helper.truncate(), view.truncate() but to no avail.
I've used the Faker gem in other parts of my tests if there's a way to generate a lorem ipsum string and truncate it to compare against somehow.
View code:
<dd><%= truncate(project.details, :length => 100) %></dd>`
Test code
it { should have_selector('dd', #project.details) }
This test test worked fine when I was showing the full details text but because I've decided to only show the first 100 characters in this view I'm not sure how to test for this without having to set the details as a fixed string and then check for a truncated version of it somehow.
Thanks
Col

Answer 1

truncate is a Rails extension to the String class and, as such, is not available in Ruby or RSpec. There may be way to "include" it in some fashion, but I'm familiar with how to do that. It turns out that the definition is self-contained, however, so defining it yourself is straightforward. Here is the source taken from http://apidock.com/rails/String/truncate. It's defined to an instance method, so if you want to use it with a string that's passed in, you'd need to include a text parameter in lieu of referencing self as is currently done in the first line of the body.
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 38
def truncate(length, options = {})
text = self.dup
options[:omission] ||= "..."
length_with_room_for_omission = length - options[:omission].mb_chars.length
chars = text.mb_chars
stop = options[:separator] ?
(chars.rindex(options[:separator].mb_chars, length_with_room_for_omission) || length_with_room_for_omission) : length_with_room_for_omission
(chars.length > length ? chars[0...stop] + options[:omission] : text).to_s
end

Answer 2

This works for me :)
require 'active_support/core_ext/string/filters'
it { should have_selector('dd', #project.details.truncate(100)) }

Answer 3

In the end I decided that if the page was being viewed on a larger screen then the wider column would allow more of the details to be shown and reduce the need for truncating the text so I decided to trim the details using css instead to reduce what was shown onscreen using the following:
.text-trim {
overflow: hidden;
white-space: nowrap;
text-overflow: ellipsis;
}