Add integration tests around OAuth login.

- There was previously a test for `saml` login in `login_spec`, but this didn't
  seem to be passing. A lot of things didn't seem right here, and I suspect that
  this test hasn't been running. I'll investigate this further.

- It took almost a whole working day to figure out this line:

    OmniAuth.config.full_host = ->(request) { request['REQUEST_URI'].sub(request['REQUEST_PATH'], '') }

  As always, it's obvious in retrospect, but it took some digging to figure out
  tests were failing and returning 404s during the callback phase.

- Test all OAuth providers - github, twitter, bitbucket, gitlab, google, and facebook

app/views/devise/shared/_omniauth_box.html.haml

@@ -6,7 +6,7 @@
     - providers.each do |provider|
       %span.light
         - has_icon = provider_has_icon?(provider)
-        = link_to provider_image_tag(provider), omniauth_authorize_path(:user, provider), method: :post, class: 'oauth-login' + (has_icon ? ' oauth-image-link' : ' btn')
+        = link_to provider_image_tag(provider), omniauth_authorize_path(:user, provider), method: :post, class: 'oauth-login' + (has_icon ? ' oauth-image-link' : ' btn'), id: "oauth-login-#{provider}"
     %fieldset
       = check_box_tag :remember_me
       = label_tag :remember_me, "Remember Me"

spec/features/oauth_login_spec.rb

@@ -0,0 +1,58 @@
+require 'spec_helper'
+
+feature 'OAuth Login', feature: true, js: true do
+  def enter_code(code)
+    fill_in 'user_otp_attempt', with: code
+    click_button 'Verify code'
+  end
+
+  def provider_config(provider)
+    OpenStruct.new(name: provider.to_s, app_id: 'app_id', app_secret: 'app_secret')
+  end
+
+  def stub_omniauth_config(provider)
+    OmniAuth.config.add_mock(provider, OmniAuth::AuthHash.new({ provider: provider.to_s, uid: "12345" }))
+    Rails.application.env_config['devise.mapping'] = Devise.mappings[:user]
+    Rails.application.env_config["omniauth.auth"] = OmniAuth.config.mock_auth[provider]
+  end
+
+  providers = [:github, :twitter, :bitbucket, :gitlab, :google_oauth2, :facebook]
+
+  before do
+    OmniAuth.config.full_host = ->(request) { request['REQUEST_URI'].sub(request['REQUEST_PATH'], '') }
+
+    messages = {
+      enabled: true,
+      allow_single_sign_on: providers.map(&:to_s),
+      providers: providers.map { |provider| provider_config(provider) }
+    }
+
+    allow(Gitlab.config.omniauth).to receive_messages(messages)
+  end
+
+  providers.each do |provider|
+    context "when the user logs in using the #{provider} provider" do
+      context "when two-factor authentication is disabled" do
+        it 'logs the user in' do
+          stub_omniauth_config(provider)
+          user = create(:omniauth_user, extern_uid: 'my-uid', provider: provider.to_s)
+          login_via(provider.to_s, user, 'my-uid')
+
+          expect(current_path).to eq root_path
+          save_screenshot
+        end
+      end
+
+      context "when two-factor authentication is enabled" do
+        it 'logs the user in' do
+          stub_omniauth_config(provider)
+          user = create(:omniauth_user, :two_factor, extern_uid: 'my-uid', provider: provider.to_s)
+          login_via(provider.to_s, user, 'my-uid')
+
+          enter_code(user.current_otp)
+          expect(current_path).to eq root_path
+        end
+      end
+    end
+  end
+end

spec/support/login_helpers.rb

@@ -62,6 +62,13 @@ module LoginHelpers
     Thread.current[:current_user] = user
   end
 
+  def login_via(provider, user, uid)
+    mock_auth_hash(provider, uid, user.email)
+    visit new_user_session_path
+    expect(page).to have_content('Sign in with')
+    click_link "oauth-login-#{provider}"
+  end
+
   def mock_auth_hash(provider, uid, email)
     # The mock_auth configuration allows you to set per-provider (or default)
     # authentication hashes to return during integration testing.