How to do proper database testing (TDD) on Rails 3 using MongoDB and Mongoid

Question

How would go about writing proper unit testing (and integration testing for that matter) using MongoDB through Mongoid on Rails ?

I am asking, because to the opposite of

Answer 1

Ok thanks to Kyle who pointed me in the right direction, I found out how to make it work.

So basically the trick is to drop all your collections in mongodb for each test case that you will run. This is a bit radical, but it works. But keep in mind that you won't retain any data at all in you test db.

Finally I found that link: http://adventuresincoding.com/2010/07/how-to-configure-cucumber-and-rspec-to-work-with-mongoid

And basically what you need to do is simple:

add a block in you spec_helper.rb:

RSpec.configure do |config|

# blabla other confs

  config.before :each do
    Mongoid.master.collections.select {|c| c.name !~ /system/ }.each(&:drop)
  end

# blabla other confs

end

For Mongoid 3:

 Mongoid.default_session.collections.select {|c| c.name !~ /system/ }.each(&:drop

This effectively kills all the collection within the db allowing you to run your tests fresh every time.

Alex

Answer 2

There's no way to make MongoDB non-persistent. You simply have to delete data before or after each test. There's some documentation on that here:

http://www.mongodb.org/display/DOCS/Rails+-+Getting+Started#Rails-GettingStarted-Testing

Answer 3

Here's what I did (using Test::Unit and Mongoid 3)...

# test/test_helper.rb
setup {
  Mongoid.default_session.collections.select {|c| c.name !~ /system/ }.each(&:drop)
}

Answer 4

Another way is to use database_cleaner. It supports multiple ORMs, so I think you could do something like this:

# spec/support/database_cleaner.rb
RSpec.configure do |config|
  config.before(:suite) do
    DatabaseCleaner[:mongoid].strategy = :truncation
    DatabaseCleaner[:mongoid].clean_with(:truncation)
  end

  config.before(:each) do
    DatabaseCleaner.start
  end

  config.after(:each) do
    DatabaseCleaner.clean
  end
end

Answer 5

This one worked for me.

In spec_helper.rb, under RSpec.configure do |config| I put:

config.before :each do
   Mongoid.purge!
end

Reference.