Merge branch 'master' of github.com:rails/docrails

1 files changed, 9 insertions, 1 deletions

diff --git a/guides/source/testing.md b/guides/source/testing.md
index bac4b63c75..c01b2e575a 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: