diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb
index f3d3cdc9e316819ead0da2245a254b51dea69fe9..6ba667b9969352516f84f054c6caa71c9b37bdc5 100644
--- a/activerecord/lib/active_record/fixtures.rb
+++ b/activerecord/lib/active_record/fixtures.rb
@@ -33,7 +33,7 @@ class FixtureClassNotFound < ActiveRecord::ActiveRecordError #:nodoc:
   # is followed by an indented list of key/value pairs in the "key: value" format. Records are
   # separated by a blank line for your viewing pleasure.
   #
-  # Note that fixtures are unordered. If you want ordered fixtures, use the omap YAML type.
+  # Note: Fixtures are unordered. If you want ordered fixtures, use the omap YAML type.
   # See http://yaml.org/type/omap.html
   # for the specification. You will need ordered fixtures when you have foreign key constraints
   # on keys in the same table. This is commonly needed for tree structures. Example:
@@ -374,8 +374,9 @@ class FixtureClassNotFound < ActiveRecord::ActiveRecordError #:nodoc:
   #
   # == Support for YAML defaults
   #
-  # You probably already know how to use YAML to set and reuse defaults in
-  # your <tt>database.yml</tt> file. You can use the same technique in your fixtures:
+  # You can set and reuse defaults in your fixtures YAML file.
+  # This is the same technique used in the <tt>database.yml</tt> file
+  # to specify defaults:
   #
   #   DEFAULTS: &DEFAULTS
   #     created_on: <%= 3.weeks.ago.to_s(:db) %>
diff --git a/guides/source/testing.md b/guides/source/testing.md
index bac4b63c75c5b8853cc21c82e96107b5ad10b1d8..c01b2e575ace5231ee8bf2b897b61ed29d8cf115 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -49,7 +49,9 @@ The `test_helper.rb` file holds the default configuration for your tests.
 
 ### The Low-Down on Fixtures
 
-For good tests, you'll need to give some thought to setting up test data. In Rails, you can handle this by defining and customizing fixtures.
+For good tests, you'll need to give some thought to setting up test data.
+In Rails, you can handle this by defining and customizing fixtures.
+You can find comprehensive documentation in the [fixture api documentation](http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html).
 
 #### What Are Fixtures?
 
@@ -94,6 +96,12 @@ one:
   category: about
 ```
 
+Note: For associations to reference one another by name, you cannot specify the `id:`
+ attribute on the fixtures. Rails will auto assign a primary key to be consistent between
+ runs. If you manually specify an `id:` attribute, this behavior will not work. For more
+  information on this assocation behavior please read the
+  [fixture api documentation](http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html).
+
 #### ERB'in It Up
 
 ERB allows you to embed Ruby code within templates. The YAML fixture format is pre-processed with ERB when Rails loads fixtures. This allows you to use Ruby to help you generate some sample data. For example, the following code generates a thousand users: