Clean up documentation

There were some grammar issues and incorrect information in the system
tests documentation.

2 files changed, 17 insertions, 16 deletions

diff --git a/actionpack/lib/action_dispatch/system_test_case.rb b/actionpack/lib/action_dispatch/system_test_case.rb
index ca23cab6ae..276e3161bd 100644
--- a/actionpack/lib/action_dispatch/system_test_case.rb
+++ b/actionpack/lib/action_dispatch/system_test_case.rb
@@ -10,7 +10,7 @@ module ActionDispatch
   class SystemTestCase < IntegrationTest
     # = System Testing
     #
-    # System tests let you test real application in the browser. Because system
+    # System tests let you test applications in the browser. Because system
     # tests use a real browser experience you can test all of your JavaScript
     # easily from your test suite.
     #
@@ -36,10 +36,10 @@ module ActionDispatch
     #     end
     #   end
     #
-    # When generating an application or scaffold a +application_system_test_case.rb+ will also
-    # be generated containing the base class for system testing. This is where you
-    # can change the driver, add Capybara settings, and other configuration for
-    # your system tests.
+    # When generating an application or scaffold a +application_system_test_case.rb+
+    # file will also be generated containing the base class for system testing.
+    # This is where you can change the driver, add Capybara settings, and other
+    # configuration for your system tests.
     #
     #   require "test_helper"
     #
@@ -51,7 +51,7 @@ module ActionDispatch
     # Selenium driver, with the Chrome browser, and a browser size of 1400x1400.
     #
     # Changing the driver configuration options are easy. Let's say you want to use
-    # and the Firefox browser instead. In your +application_system_test_case.rb+
+    # the Firefox browser instead of Chrome. In your +application_system_test_case.rb+
     # file add the following:
     #
     #   require "test_helper"
@@ -61,8 +61,9 @@ module ActionDispatch
     #   end
     #
     # +driven_by+ has a required argument for the driver name. The keyword
-    # arguments are +:using+ for the browser (not applicable for headless drivers),
-    # and +:screen_size+ to change the size of the screen taking screenshots.
+    # arguments are +:using+ for the browser and +:screen_size+ to change the
+    # size of the browser screen. These two options are not applicable for
+    # headless drivers and will be silently ignored if passed.
     #
     # To use a headless driver, like Poltergeist, update your Gemfile to use
     # Poltergeist instead of Selenium and then declare the driver name in the
@@ -93,7 +94,7 @@ module ActionDispatch
 
     # System Test configuration options
     #
-    # The defaults settings are Selenium, using Chrome, with a screen size
+    # The default settings are Selenium, using Chrome, with a screen size
     # of 1400x1400.
     #
     # Examples:
diff --git a/guides/source/testing.md b/guides/source/testing.md
index fe0dbf6c50..c7897a42a1 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -628,8 +628,8 @@ end
 ```
 
 By default, system tests are run with the Selenium driver, using the Chrome
-browser, on port 21800 with Puma, and a screen size of 1400x1400. The next
-section explains how to change the default settings.
+browser, and a screen size of 1400x1400. The next section explains how to
+change the default settings.
 
 ### Changing the default settings
 
@@ -654,7 +654,7 @@ class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
 end
 ```
 
-If you want to keep the Selenium driver but change the browser or port you
+If you want to keep the Selenium driver but change the browser you
 can pass Firefox and the port to driven by. The driver is a required
 argument, all other arguments are optional.
 
@@ -662,7 +662,7 @@ argument, all other arguments are optional.
 require "test_helper"
 
 class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
-  driven_by :selenium, using: :firefox, on: 3000
+  driven_by :selenium, using: :firefox
 end
 ```
 
@@ -680,13 +680,13 @@ for additional settings.
 
 ### Screenshot Helper
 
-The `ScreenshotHelper` is a helper designed to capture screenshots of your test.
+The `ScreenshotHelper` is a helper designed to capture screenshots of your tests.
 This can be helpful for viewing the browser at the point a test failed, or
 to view screenshots later for debugging.
 
 Two methods are provided: `take_screenshot` and `take_failed_screenshot`.
-`take_failed_screenshot` is automatically included in the `application_system_test_case.rb`
-file and will take a screenshot only if the test fails.
+`take_failed_screenshot` is automatically included in  `after_teardown` inside
+Rails.
 
 The `take_screenshot` helper method can be included anywhere in your tests to
 take a screenshot of the browser.