Improve the testing guide [ci skip]

Improve the "Testing Rails Applications" guide adding a section for
testing helpers and a little note about associations with ActiveRecord
and YAML fixtures.

Also add a link to Fixture Builder ; yet another replacement for
fixtures such as Machinist or FactoryGirl.

1 files changed, 64 insertions, 6 deletions

diff --git a/guides/source/testing.md b/guides/source/testing.md
index 416a8b592f..590728cf14 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -66,18 +66,34 @@ Here's a sample YAML fixture file:
 ```yaml
 # lo & behold! I am a YAML comment!
 david:
- name: David Heinemeier Hansson
- birthday: 1979-10-15
- profession: Systems development
+  name: David Heinemeier Hansson
+  birthday: 1979-10-15
+  profession: Systems development
 
 steve:
- name: Steve Ross Kellock
- birthday: 1974-09-27
- profession: guy with keyboard
+  name: Steve Ross Kellock
+  birthday: 1974-09-27
+  profession: guy with keyboard
 ```
 
 Each fixture is given a name followed by an indented list of colon-separated key/value pairs. Records are typically separated by a blank space. You can place comments in a fixture file by using the # character in the first column. Keys which resemble YAML keywords such as 'yes' and 'no' are quoted so that the YAML Parser correctly interprets them.
 
+If you are working with [associations](/association_basics.html), you can simply
+define a reference node between two different fixtures. Here's an example with
+a belongs_to/has_many association:
+
+```yaml
+# In fixtures/categories.yml
+about:
+  name: About
+
+# In fixtures/articles.yml
+one:
+  title: Welcome to Rails!
+  body: Hello world!
+  category: about
+```
+
 #### 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:
@@ -990,6 +1006,47 @@ class UserControllerTest < ActionController::TestCase
 end
 ```
 
+Testing helpers
+---------------
+
+In order to test helpers, all you need to do is check that the output of the
+helper method matches what you'd expect. Tests related to the helpers are
+located under the `test/helpers` directory. Rails provides a generator which
+generates both the helper and the test file:
+
+```bash
+$ rails generate helper User
+      create  app/helpers/user_helper.rb
+      invoke  test_unit
+      create    test/helpers/user_helper_test.rb
+```
+
+The generated test file contains the following code:
+
+```ruby
+require 'test_helper'
+
+class UserHelperTest < ActionView::TestCase
+end
+```
+
+A helper is just a simple module where you can define methods which are
+available into your views. To test the output of the helper's methods, you just
+have to use a mixin like this:
+
+```ruby
+class UserHelperTest < ActionView::TestCase
+  include UserHelper
+
+  test "should return the user name" do
+    # ...
+  end
+end
+```
+
+Moreover, since the test class extends from `ActionView::TestCase`, you have
+access to Rails' helper methods such as `link_to` or `pluralize`.
+
 Other Testing Approaches
 ------------------------
 
@@ -998,6 +1055,7 @@ The built-in `test/unit` based testing is not the only way to test Rails applica
 * [NullDB](http://avdi.org/projects/nulldb/), a way to speed up testing by avoiding database use.
 * [Factory Girl](https://github.com/thoughtbot/factory_girl/tree/master), a replacement for fixtures.
 * [Machinist](https://github.com/notahat/machinist/tree/master), another replacement for fixtures.
+* [Fixture Builder](https://github.com/rdy/fixture_builder), a tool that compiles Ruby factories into fixtures before a test run.
 * [MiniTest::Spec Rails](https://github.com/metaskills/minitest-spec-rails), use the MiniTest::Spec DSL within your rails tests.
 * [Shoulda](http://www.thoughtbot.com/projects/shoulda), an extension to `test/unit` with additional helpers, macros, and assertions.
 * [RSpec](http://relishapp.com/rspec), a behavior-driven development framework