Transactions

When you run rails generate rspec:install, the spec/rails_helper.rb file includes the following configuration:

RSpec.configure do |config|
  config.use_transactional_fixtures = true
end

The name of this setting is a bit misleading. What it really means in Rails is “run every test method within a transaction.” In the context of rspec-rails, it means “run every example within a transaction.”

The idea is to start each example with a clean database, create whatever data is necessary for that example, and then remove that data by simply rolling back the transaction at the end of the example.

Disabling transactions

If you prefer to manage the data yourself, or using another tool like database_cleaner to do it for you, simply tell RSpec to tell Rails not to manage transactions:

RSpec.configure do |config|
  config.use_transactional_fixtures = false
end

Data created in before(:example) are rolled back

Any data you create in a before(:example) hook will be rolled back at the end of the example. This is a good thing because it means that each example is isolated from state that would otherwise be left around by the examples that already ran. For example:

describe Widget do
  before(:example) do
    @widget = Widget.create
  end

  it "does something" do
    expect(@widget).to do_something
  end

  it "does something else" do
    expect(@widget).to do_something_else
  end
end

The @widget is recreated in each of the two examples above, so each example has a different object, and the underlying data is rolled back so the data backing the @widget in each example is new.

Data created in before(:context) are not rolled back

before(:context) hooks are invoked before the transaction is opened. You can use this to speed things up by creating data once before any example in a group is run, however, this introduces a number of complications and you should only do this if you have a firm grasp of the implications. Here are a couple of guidelines:

1. Be sure to clean up any data in an after(:context) hook:

   before(:context) do
     @widget = Widget.create!
   end
   
   after(:context) do
     @widget.destroy
   end
   

   If you don’t do that, you’ll leave data lying around that will eventually interfere with other examples.

2. Reload the object in a before(:example) hook.

   before(:context) do
     @widget = Widget.create!
   end
   
   before(:example) do
     @widget.reload
   end
   

Even though database updates in each example will be rolled back, the object won’t know about those rollbacks so the object and its backing data can easily get out of sync.