Capybara is not loading the routing helpers. Use explicit paths

Perhaps a file is not being required somewhere, but I was getting

    1) Tweet responds to html
         Failure/Error: visit tweets_path
         NameError:
           undefined local variable or method `tweets_path' for #<RSpec::Core::ExampleGroup::Nested_1:0x007fb42d4779d8>
         # ./spec/features/tweets_spec.rb:14:in `block (2 levels) in <top (required)>'

So I've made the paths explicit, so that the tests pass.