SlowFactoryFormatter

This gem is a custom RSpec formatter that allows you to generate a table of slow factories when you run your tests.

FactoryGirl uses ActiveSupport::Notifications instrumentation api which allows us track how much time is spent creating factories.

This gem uses that api to display factories that take a long to setup.

My naive definition of a slow factory is any factory that takes more then 0.5 seconds to setup or any factory that creates or builds more then five instances of itself. If a factory does either of those things then SlowFactoryFormatter will generate a table and add that factory as a row to that table.

FactoryGirl allows you to quickly and painlessly setup factories that you can use in your tests. You can then use them in your tests by calling FactoryGirl.(build || create)(:some_factory) and create a tree of objects, when really you only meant to create/instantiate one object for your test. When you try to use a factory that sets up a lot of objects in a simple test case, you'll end up slowing down your test suite, unaware that the reason why your test suite has slowed down is because how many objects are being setup in the background.

This can quickly increase the time it takes a test suite to run and as a team grows it can really start to slowdown the build.

I've seen projects where one of the main causes of a slow build is the number of factories being setup in each example group.

The main benefit of using SlowFactoryFormatter is that it will help you identify the number of objects being setup, when you run a test.

This gem is intended to be used on a Rails project and you will need to have FactoryGirl, RSpec version 3.4 or later and ActiveSupport version 3 or later in your project.

To use this gem with a Rails project add this line to your Gemfile:

group :test do
  gem 'slow_factory_formatter'
end

And then run:

`$ bundle`

Or install it yourself as:

`$ gem install slow_factory_formatter`

You can either use this gem when running rspec command:

rspec spec/models/user_spec --format SlowFactoryFormatter

+------------------------------+--------+-------+---------------+----------------------+
|                                    Slow Factories                                    |
+------------------------------+--------+-------+---------------+----------------------+
| Factory Name                 | Create | Build | Build Stubbed | Total Time           |
+------------------------------+--------+-------+---------------+----------------------+
| user                         | 67     | 2     | 16            | 4.48 seconds         |
| product                      | 45     | 0     | 2             | 1.16 seconds         |
| order                        | 97     | 0     | 0             | 3.66 seconds         |
| admin                        | 49     | 12    | 1             | 3.02 seconds         |
| project                      | 33     | 40    | 34            | 4.33 seconds         |
| customer                     | 88     | 43    | 2             | 6.16 seconds         |
| manager                      | 12     | 23    | 0             | 1.10 seconds         |
+------------------------------+--------+-------+---------------+----------------------+

Or if you want to use it every time you run a test in your project, you can add it to .rspec file in the root of your project directory:

--format SlowFactoryFormatter

This will make SlowFactoryFormatter your default formatter and you'll see a table similar to the one above of slow factories whenever you run a test, unless you have no slow factories.

Michael Baldry initially introduced me to the idea of generating a table of slow factories.

Tom Stuart suggested I turn this into a simple gem that can be reused on many projects.

Bug reports and pull requests are welcome on GitHub at https://github.com/mrageh/slow_factory_formatter.

The gem is available as open source under the terms of the MIT License.