Testing Model Associations in Rspec (Rails 3)
I live with five really awesome housemates. Five warm bodies tend to make a mess by the end of the week so we have a chore chart on the fridge. I tend to be the one who badgers everyone else into doing their weekly chore - not my favorite thing to do...so, I figure it's time to put Rails to work sending those emails for me.
I named our fridge chore chart replacement Choretle. I'm excited to get it finished so that it can do all the dirty work of emailing reminders and doling out appropriate praise for a job well done.
I've got my data model pretty much sorted out at this point and I just started generating my models. I decided to do some googling about testing model associations since it has never been as streamlined as I'd like. I found a couple of ways to test associations, some of them better than others.
The way I've tested associations in the past has gone something like this:
describe Group do
it "should respond to users" do
g = Group.new
g.should respond_to(:users)
end
end
What I don't like about it is that it is a round-about way of testing for an association. It tests a side effect of the association, not that the association exists.
The next solution I found is built into ActiveRecord::Reflection::AssociationReflection, so no need to install extra gems:
> g = Group.reflect_on_association(:users)
=> #<ActiveRecord::Reflection::ThroughReflection:0x00000100d65208 @macro=:has_many, @name=:users, @options={:through=>:affiliations, :extend=>[]}, @active_record=Group(id: integer, name: string, creator: integer, created_at: datetime, updated_at: datetime), @collection=true>
> g.macro
=> :has_many
The macro method makes it fairly easy to write an
association test:
describe Group do
it "should have many users" do
g = Group.reflect_on_association(:users)
g.macro.should == :has_many
end
end
It is still kinda ugly don't you think? Definitely not an elegant way to indicate the relationship. Luckily, I found a couple of recommendations for gems that make for more descriptive syntax: remarkable and shoulda. Both gems have similar syntax:
#both remarkable and shoulda use this syntax
describe Group do
it { should belong_to(:supergroup) }
it { should have_many(:users) }
end
Remarkable seems cool, but from what I could tell, it isn't well maintained. The last commit is from about a year ago on the carlosbrando fork.
I decided to use Shoulda for my tests. It's easy to get working - just
add gem 'shoulda-matchers' to the Gemfile.
Here is my (short and symantically relevent) model association test:
describe Group do
it { should have_many(:users)}
end
In my research, I encountered some debate about whether testing associations is worthwhile in the first place. Some people argue that it is testing Rails instead of your own code. I'd argue that testing associations isn't testing Rails. It is testing that your code is hooked up the way you want it. Testing associations also gets me into the TDD frame of mind as soon as I start a project. Plus, when Shoulda makes it so easy, I don't have any excuses not to test associations.
