Adding travis rails build matrix

posts/2013-03-10-travis-build-matrix-for-rails.md

@@ -0,0 +1,56 @@
+---
+title: "Travis build matrix for Rails"
+date: 2013-03-10 14:06
+---
+
+Do you have a gem that needs to test against multiple versions of Rails? Doing
+it all can be complex, and while I have lots to say about this topic, but
+here's one of the pieces: Travis build matrix.
+
+Here's what you want:
+
+```
+anguage: ruby
+rvm:
+  - 1.8.7
+  - 1.9.2
+  - 1.9.3
+  - 2.0.0
+  - ruby-head
+env:
+  - "RAILS_VERSION=3.2"
+  - "RAILS_VERSION=3.1"
+  - "RAILS_VERSION=3.0"
+  - "RAILS_VERSION=master"
+matrix:
+  allow_failures:
+    - rvm: ruby-head
+    - env: "RAILS_VERSION=master"
+  exclude:
+    - rvm: 2.0.0
+      env: "RAILS_VERSION=3.0"
+    - rvm: 2.0.0
+      env: "RAILS_VERSION=3.1"
+    - rvm: 1.8.7
+      env: "RAILS_VERSION=master"
+    - rvm: 1.9.2
+      env: "RAILS_VERSION=master"
+    - rvm: ruby-head
+      env: "RAILS_VERSION=3.0"
+    - rvm: ruby-head
+      env: "RAILS_VERSION=3.1"
+```
+
+Here's what all this does:
+
+1. 1.8.7 and 1.9.2 is supported across all of the 3.x series, but not master
+2. 2.0.0 is supported on Rails 3.2 (as of the upcoming 3.2.13, but it will
+   probably work with your gem with 3.2.12) and master, but not 3.0 or 3.1.
+3. We want to allow failures on ruby-head, because it's not likely to be stable
+4. We also want to allow failures for Rails master, because sometimes it's not
+   stable either
+5. ruby-head should only be built against master
+
+
+What do you think? [Tweet at me](http://twitter.com/steveklabnik) if you have
+suggestions for improving this matrix.