assert_difference has morphed

This is just a little note that assert_difference, the ultimate test helper, has been merged into core. The only issue is that it has changed a bit from the version that I have used. I always used something along the lines of:

assert_difference Post, :count do
  Post.create_valid
end

The version that got merged into core instead accepts a string like so:

assert_difference 'Post.count' do
  Post.create_valid
end

Not sure why the syntax is different but that is neither here nor there for me. The only down side is I had to go through all my tests and fix the incorrect arguments. Just thought I would say something here so others know what is going wrong when all their tests fail after upgrading to edge.

3 Comments

DHH
May 28, 2007

Try asserting the difference on post.comments.size with the old syntax and you’ll see why it changed ;)
John Nunemaker
May 28, 2007

Well, I trusted that it was for the best. :) Thanks for the example.
so
Dec 19, 2007

I’m using Rails 2.0.1 and the ‘Post.count’ syntax doesn’t seem to be working. I get TypeError: nil is not a symbol. The old syntax works though :-)