6 files changed, 34 insertions, 5 deletions
diff --git a/guides/rails_guides/markdown/renderer.rb b/guides/rails_guides/markdown/renderer.rb
index 82bb4d6de1..f186ac526f 100644
--- a/guides/rails_guides/markdown/renderer.rb
+++ b/guides/rails_guides/markdown/renderer.rb
@@ -31,7 +31,7 @@ HTML
 
         header_with_id = text.scan(/(.*){#(.*)}/)
         unless header_with_id.empty?
-          %(<h#{header_level} id=#{header_with_id[0][1].strip}>#{header_with_id[0][0].strip}</h#{header_level}>)
+          %(<h#{header_level} id="#{header_with_id[0][1].strip}">#{header_with_id[0][0].strip}</h#{header_level}>)
         else
           %(<h#{header_level}>#{text}</h#{header_level}>)
         end
diff --git a/guides/source/action_cable_overview.md b/guides/source/action_cable_overview.md
index 14c859994c..e6c0ae31a8 100644
--- a/guides/source/action_cable_overview.md
+++ b/guides/source/action_cable_overview.md
@@ -665,7 +665,7 @@ The above will start a cable server on port 28080.
 
 The WebSocket server doesn't have access to the session, but it has
 access to the cookies. This can be used when you need to handle
-authentication. You can see one way of doing that with Devise in this [article](http://www.rubytutorial.io/actioncable-devise-authentication).
+authentication. You can see one way of doing that with Devise in this [article](https://greg.molnar.io/blog/actioncable-devise-authentication/).
 
 ## Dependencies
 
diff --git a/guides/source/active_storage_overview.md b/guides/source/active_storage_overview.md
index 71ba6184e0..d5387219f5 100644
--- a/guides/source/active_storage_overview.md
+++ b/guides/source/active_storage_overview.md
@@ -82,6 +82,14 @@ To use the Amazon S3 service in production, you add the following to
 config.active_storage.service = :amazon
 ```
 
+To use the test service when testing, you add the following to
+`config/environments/test.rb`:
+
+```ruby
+# Store uploaded files on the local file system in a temporary directory.
+config.active_storage.service = :test
+```
+
 Continue reading for more information on the built-in service adapters (e.g.
 `Disk` and `S3`) and the configuration they require.
 
diff --git a/guides/source/active_support_instrumentation.md b/guides/source/active_support_instrumentation.md
index 9963125fa2..64db141381 100644
--- a/guides/source/active_support_instrumentation.md
+++ b/guides/source/active_support_instrumentation.md
@@ -623,7 +623,7 @@ The block receives the following arguments:
 * The name of the event
 * Time when it started
 * Time when it finished
-* A unique ID for this event
+* A unique ID for the instrumenter that fired the event
 * The payload (described in previous sections)
 
 ```ruby
@@ -672,7 +672,8 @@ Creating custom events
 Adding your own events is easy as well. `ActiveSupport::Notifications` will take care of
 all the heavy lifting for you. Simply call `instrument` with a `name`, `payload` and a block.
 The notification will be sent after the block returns. `ActiveSupport` will generate the start and end times
-as well as the unique ID. All data passed into the `instrument` call will make it into the payload.
+and add the instrumenter's unique ID. All data passed into the `instrument` call will make 
+it into the payload.
 
 Here's an example:
 
diff --git a/guides/source/contributing_to_ruby_on_rails.md b/guides/source/contributing_to_ruby_on_rails.md
index 9f768c3544..ed47a0de0f 100644
--- a/guides/source/contributing_to_ruby_on_rails.md
+++ b/guides/source/contributing_to_ruby_on_rails.md
@@ -336,6 +336,26 @@ $ bundle exec ruby -w -Itest test/mail_layout_test.rb -n test_explicit_class_lay
 The `-n` option allows you to run a single method instead of the whole
 file.
 
+#### Running tests with a specific seed
+
+Test execution is randomized with a randomization seed. If you are experiencing random
+test failures you can more accurately reproduce a failing test scenario by specifically
+setting the randomization seed.
+
+Running all tests for a component:
+
+```bash
+$ cd actionmailer
+$ SEED=15002 bundle exec rake test
+```
+
+Running a single test file:
+
+```bash
+$ cd actionmailer
+$ SEED=15002 bundle exec ruby -w -Itest test/mail_layout_test.rb
+```
+
 #### Testing Active Record
 
 First, create the databases you'll need. You can find a list of the required
diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md
index 9eb77d2a50..e2f558d74c 100644
--- a/guides/source/getting_started.md
+++ b/guides/source/getting_started.md
@@ -126,7 +126,7 @@ run the following:
 $ rails --version
 ```
 
-If it says something like "Rails 5.1.1", you are ready to continue.
+If it says something like "Rails 5.2.1", you are ready to continue.
 
 ### Creating the Blog Application