Update CONTRIBUTING

[ci skip]

CONTRIBUTING.md

@@ -13,16 +13,12 @@ request.
 1. Now that you've cloned the repo, navigate to it and install dependencies by
    running:
 
-   ```
-   bundle install
-   ```
+      bundle install
 
 1. All tests should be passing, but it's a good idea to run them anyway
    before starting any work:
-   
-   ```
-   bundle exec rake
-   ```
+
+      bundle exec rake
 
 1. If you're adding functionality or fixing a bug, you'll want to add a
    failing test for the issue first.
@@ -33,34 +29,42 @@ request.
    run the tests again. Since you're probably working on a single file, you can
    run the tests for that file with the following command:
 
-   ```
-   appraisal 4.2 rspec <path of test file to run>
-   ```
+      bundle exec appraisal <Appraisal name> rspec <path of test file to run>
 
-   You can also run unit tests by running `zeus start` in one shell, and then
-   running the following in another:
+   You can find a list of valid Appraisals by running:
 
-   ```
-   zeus rspec <path of test file to run>
-   ```
+      bundle exec rake appraisal:list
 
-   And to run the entire test suite again:
-   
-   ```
-   bundle exec rake
-   ```
+   (If you're familiar with Zeus, you can also run unit tests by running `zeus
+   start` in one shell, and then running the following in another:)
+
+      zeus rspec <path of test file to run>
+
+   In any case, to run the entire test suite again, say:
+
+      bundle exec rake
 
 1. Finally, push to your fork and submit a pull request.
 
-At this point you're waiting on us. We try to respond to issues and pull
-requests within a few business days. We may suggest some changes to make to your
-code to fit with our [code style] or the project style, or discuss alternate
-ways of addressing the issue in question. When we're happy with everything,
-we'll bring your changes into master. Now you're a contributor!
+At this point, you're waiting on us. We may suggest some changes to make to your
+code to fit within the project style, or discuss alternate ways of addressing
+the issue in question. When we're happy with everything, we'll bring your
+changes into master. Now you're a contributor!
 
 ## Addendum: Setting up your environment
 
-### Installing dependencies (Linux only)
+### Installing Ruby
+
+shoulda-matchers is only compatible with Ruby 2.x. A `.ruby-version` is included
+in the repo, so if you're using one of the Ruby version manager tools, then you
+should be using (or have been prompted to install) the latest version of Ruby.
+If not, you'll want to do that.
+
+[working Ruby environment]: #addendum-setting-up-your-environment
+[Code of Conduct]: https://thoughtbot.com/open-source-code-of-conduct
+[execjs]: https://github.com/sstephenson/execjs
+
+### Linux-specific instructions
 
 #### Debian/Ubuntu
 
@@ -86,16 +90,3 @@ sudo su
 curl -sL https://rpm.nodesource.com/setup | bash -
 yum install -y nodejs
 ```
-
-### Installing Ruby (all platforms)
-
-shoulda-matchers is only compatible with Ruby 2.x. A `.ruby-version` is included
-in the repo, so if you're using one of the Ruby version manager tools, then you
-should be using (or have been prompted to install) the latest version of Ruby.
-If not, you'll want to do that.
-
-[working Ruby environment]: #addendum-setting-up-your-environment
-[Code of Conduct]: https://thoughtbot.com/open-source-code-of-conduct
-[code style]: https://github.com/thoughtbot/guides/tree/master/style
-[execjs]: https://github.com/sstephenson/execjs
-[install rvm]: https://rvm.io/rvm/install

Rakefile

@@ -34,6 +34,13 @@ task :default do
   end
 end
 
+namespace :appraisal do
+  task :list do
+    appraisals = Tests::CurrentBundle.instance.available_appraisals
+    puts "Valid appraisals: #{appraisals.join(', ')}"
+  end
+end
+
 Shoulda::Matchers::DocumentationTasks.create
 
 task release: 'docs:publish_latest'