Add cop for Capybara expectations set on current_path

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Master (Unreleased)
 
 * Fix false positive in `Capybara/FeatureMethods`. ([@Darhazer][])
+* Add `RSpec/Capybara/CurrentPathExpectation` cop for feature specs, disallowing setting expectations on `current_path`. ([@timrogers][])
 
 ## 1.17.1 (2017-09-20)
 
@@ -250,3 +251,4 @@
 [@pocke]: https://github.com/pocke
 [@bmorrall]: https:/github.com/bmorrall
 [@zverok]: https:/github.com/zverok
+[@timrogers]: https://github.com/timrogers

config/default.yml

@@ -325,6 +325,11 @@ RSpec/VoidExpect:
   Enabled: true
   StyleGuide: http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/VoidExpect
 
+Capybara/CurrentPathExpectation:
+  Description: Checks that no expectations are set on Capybara's `current_path`.
+  Enabled: true
+  StyleGuide: http://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/Capybara/CurrentPathExpectation
+
 Capybara/FeatureMethods:
   Description: Checks for consistent method usage in feature specs.
   Enabled: true

lib/rubocop-rspec.rb

@@ -29,6 +29,7 @@
 require 'rubocop/cop/rspec/around_block'
 require 'rubocop/cop/rspec/be_eql'
 require 'rubocop/cop/rspec/before_after_all'
+require 'rubocop/cop/rspec/capybara/current_path_expectation'
 require 'rubocop/cop/rspec/capybara/feature_methods'
 require 'rubocop/cop/rspec/describe_class'
 require 'rubocop/cop/rspec/describe_method'

lib/rubocop/cop/rspec/capybara/current_path_expectation.rb

@@ -0,0 +1,42 @@
+module RuboCop
+  module Cop
+    module RSpec
+      module Capybara
+        # Checks that no expectations are set on Capybara's `current_path`.
+        #
+        # The `have_current_path` matcher (http://www.rubydoc.info/github/
+        # teamcapybara/capybara/master/Capybara/RSpecMatchers#have_current_path-
+        # instance_method) should be used on `page` to set expectations on
+        # Capybara's current path, since it uses Capybara's waiting
+        # functionality (https://github.com/teamcapybara/capybara/blob/master/
+        # README.md#asynchronous-javascript-ajax-and-friends) which ensures that
+        # preceding actions (like `click_link`) have completed.
+        #
+        # @example
+        #   # bad
+        #   expect(current_path).to eq('/callback')
+        #   expect(page.current_path).to match(/widgets/)
+        #
+        #   # good
+        #   expect(page).to have_current_path("/callback")
+        #   expect(page).to have_current_path(/widgets/)
+        #
+        class CurrentPathExpectation < Cop
+          MSG = 'Do not set an RSpec expectation on `current_path` in ' \
+                'Capybara feature specs - instead, use the ' \
+                '`have_current_path` matcher on `page`'.freeze
+
+          def_node_matcher :expectation_set_on_current_path, <<-PATTERN
+            (send nil :expect (send {(send nil :page) nil} :current_path))
+          PATTERN
+
+          def on_send(node)
+            expectation_set_on_current_path(node) do
+              add_offense(node, :selector)
+            end
+          end
+        end
+      end
+    end
+  end
+end

spec/rubocop/cop/rspec/capybara/current_path_expectation_spec.rb

@@ -0,0 +1,29 @@
+RSpec.describe RuboCop::Cop::RSpec::Capybara::CurrentPathExpectation do
+  subject(:cop) { described_class.new }
+
+  it 'flags violations for `expect(current_path)`' do
+    expect_offense(<<-RUBY)
+      expect(current_path).to eq("/callback")
+      ^^^^^^ Do not set an RSpec expectation on `current_path` in Capybara feature specs - instead, use the `have_current_path` matcher on `page`
+    RUBY
+  end
+
+  it 'flags violations for `expect(page.current_path)`' do
+    expect_offense(<<-RUBY)
+      expect(page.current_path).to eq("/callback")
+      ^^^^^^ Do not set an RSpec expectation on `current_path` in Capybara feature specs - instead, use the `have_current_path` matcher on `page`
+    RUBY
+  end
+
+  it "doesn't flag a violation for other expectations" do
+    expect_no_offenses(<<-RUBY)
+      expect(current_user).to eq(user)
+    RUBY
+  end
+
+  it "doesn't flag a violation for other references to `current_path`" do
+    expect_no_offenses(<<-RUBY)
+      current_path = WalkingRoute.last.path
+    RUBY
+  end
+end