Regression Test Selection

This is a demo repository for regression test selection. You will need Ruby 2.3 to use this (which is currently trunk Ruby).

Make it go with Minitest

To try it with Minitest, do:

$ COLLECTION=1 ruby -I lib spec/whatever_test.rb

This will create the initial coverage information. Then modify lib/my_thing.rb so that the diff looks like this:

diff --git a/lib/my_thing.rb b/lib/my_thing.rb
index 806deff..eb057b9 100644
--- a/lib/my_thing.rb
+++ b/lib/my_thing.rb
@@ -4,7 +4,7 @@ class Whatever
   end
 
   def bar
-    "bar #{@foo}"
+    raise
   end
 
   def baz

Now to predict which tests will fail, do this:

$ ruby what_to_run.rb

Make it go with RSpec

To try it with RSpec, do:

$ COLLECTION=1 rspec spec/whatever_spec.rb

This will create the initial coverage information. Then modify lib/my_thing.rb so that the diff looks like this:

diff --git a/lib/my_thing.rb b/lib/my_thing.rb
index 806deff..eb057b9 100644
--- a/lib/my_thing.rb
+++ b/lib/my_thing.rb
@@ -4,7 +4,7 @@ class Whatever
   end
 
   def bar
-    "bar #{@foo}"
+    raise
   end
 
   def baz

Now to predict which tests will fail, do this:

$ ruby what_to_run.rb