How do I test helpers in Rails 4? - ruby-on-rails

Question

With this ApplicationHelper:
class ApplicationHelper
def my_method
link_to 'foo', 'bar'
end
end
and this application_helper_spec:
require 'rails_helper'
describe ApplicationHelper do
describe 'links' do
it 'should call a helper method' do
expect(helper.my_method).to eq("<a href='bar'>foo</a>")
end
end
end
I'm having trouble getting things to work as as I expected from the latest documentation I can find on Rails helper specs. (The docs are for Ruby 3 and I'm using 4.) There doesn't appear to be a helper object:
undefined local variable or method `helper' for #<RSpec::ExampleGroups::ApplicationHelper::Links:0x007fda1895c2f8>
If instead I do this:
require 'rails_helper'
include ApplicationHelper
describe ApplicationHelper do
describe 'links' do
it 'should call a helper method' do
expect(my_method).to eq("<a href='bar'>foo</a>")
end
end
end
now my_method is called correctly but link_to is not defined:
undefined method `link_to' for #<RSpec::ExampleGroups::ApplicationHelper::Links:0x007fda1c4c3e90>
(This latter case is the same as if I define config.include ApplicationHelper in rails_helper.)
Obviously the spec environment does not include all the standard Rails helpers. What am I doing wrong here?

Answer 1

You need to either enable the infer_spec_type_from_file_location! option, or explicitly set the test type, e.g.:
describe ApplicationHelper, type: :helper do
...
end

Answer 2

I think that Andy Waite's answer regarding defining type: :helper on your spec is correct in that it will solve your undefined local variable or method 'helper' issues.
However, as for the overarching question of "How do I test helpers in Rails 4?", and specifically your method that seems to just make a call to ActionView::Helpers::UrlHelper#link_to, assuming that you don't want to cover this in a feature spec and want to test it in isolation, consider that if you want to test that "calling #my_method returns a string containing HTML for a foo bar link", the link_to tests for UrlHelper itself would confirm that calling link_to 'foo', 'bar' will return "<a href='bar'>foo</a>".
So, I'd suggest moving your specs up one level higher, saying that you want to test that "calling #my_method returns me a link for foo bar (in whatever way Rails hands me back links)":
require 'rails_helper'
RSpec.describe ApplicationHelper, type: :helper do
describe '#my_method' do
it 'returns a foo bar link' do
expect(helper).to receive(:link_to).with('foo', 'bar')
helper.my_method
end
end
end
Personally though, I don't think this method has enough logic in it to warrant testing in isolation in a helper spec, and you'd be better off covering it in a feature spec where I assume you'd be testing for the display of the link, or clicking it to see what happens etc.