Bump Capybara and include Minitest::Assertions

Capybara was updated in teamcapybara/capybara#1841 to use Minitest style
assertions so that system test output shows x number of assertions, x
numbe of failures, etc.

Before:

```
6 runs, 0 assertions, 0 failures, 0 errors, 0 skips
```

After:

```
6 runs, 7 assertions, 1 failures, 0 errors, 0 skips
```

This change bumps Capybara from 2.7.0 to 2.13.0 and includes the
required minitest assertion file in the test case. 🎉

Gemfile

@@ -14,7 +14,7 @@ gem "rake", ">= 11.1"
 # be loaded after loading the test library.
 gem "mocha", "~> 0.14", require: false
 
-gem "capybara", "~> 2.7.0"
+gem "capybara", "~> 2.13.0"
 
 gem "rack-cache", "~> 1.2"
 gem "jquery-rails"

Gemfile.lock

@@ -120,7 +120,7 @@ GEM
     bunny (2.6.2)
       amq-protocol (>= 2.0.1)
     byebug (9.0.6)
-    capybara (2.7.1)
+    capybara (2.13.0)
       addressable
       mime-types (>= 1.16)
       nokogiri (>= 1.3.3)
@@ -377,7 +377,7 @@ DEPENDENCIES
   blade
   blade-sauce_labs_plugin
   byebug
-  capybara (~> 2.7.0)
+  capybara (~> 2.13.0)
   coffee-rails
   dalli (>= 2.2.1)
   delayed_job

actionpack/lib/action_dispatch/system_test_case.rb

 require "capybara/dsl"
+require "capybara/minitest"
 require "action_controller"
 require "action_dispatch/system_testing/driver"
 require "action_dispatch/system_testing/server"
@@ -80,6 +81,7 @@ module ActionDispatch
   # tests as long as you include the required gems and files.
   class SystemTestCase < IntegrationTest
     include Capybara::DSL
+    include Capybara::Minitest::Assertions
     include SystemTesting::TestHelpers::SetupAndTeardown
     include SystemTesting::TestHelpers::ScreenshotHelper
 

railties/lib/rails/generators/rails/app/templates/Gemfile

@@ -34,7 +34,7 @@ group :development, :test do
   gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
   <%- unless options.skip_system_test? || options.api? -%>
   # Adds support for Capybara system testing and selenium driver
-  gem 'capybara', '~> 2.7.0'
+  gem 'capybara', '~> 2.13.0'
   gem 'selenium-webdriver'
   <%- end -%>
 end