Factory Doctor

One common bad pattern that slows our tests down is unnecessary database manipulation. Consider a bad example:

# with FactoryBot/FactoryGirl
it "validates name presence" do
  user = create(:user)
  user.name = ""
  expect(user).not_to be_valid
end

# with Fabrication
it "validates name presence" do
  user = Fabricate(:user)
  user.name = ""
  expect(user).not_to be_valid
end

Here we create a new user record, run all callbacks and validations and save it to the database. We don't need all these! Here is a good example:

# with FactoryBot/FactoryGirl
it "validates name presence" do
  user = build_stubbed(:user)
  user.name = ""
  expect(user).not_to be_valid
end

# with Fabrication
it "validates name presence" do
  user = Fabricate.build(:user)
  user.name = ""
  expect(user).not_to be_valid
end

Read more about build_stubbed.

FactoryDoctor is a tool that helps you identify such bad tests, i.e. tests that perform unnecessary database queries.

Example output:

[TEST PROF INFO] FactoryDoctor report

Total (potentially) bad examples: 2
Total wasted time: 00:13.165

User (./spec/models/user_spec.rb:3) (3 records created, 00:00.628)
  validates name (./spec/user_spec.rb:8) – 1 record created, 00:00.114
  validates email (./spec/user_spec.rb:8) – 2 records created, 00:00.514

NOTE: have you noticed the "potentially" word? Unfortunately, FactoryDoctor is not a magician (it's still learning) and sometimes it produces false negatives and false positives too.

Please, submit an issue if you found a case which makes FactoryDoctor fail.

You can also tell FactoryDoctor to ignore specific examples/groups. Just add the :fd_ignore tag to it:

# won't be reported as offense
it "is ignored", :fd_ignore do
  user = create(:user)
  user.name = ""
  expect(user).not_to be_valid
end

Instructions

FactoryDoctor supports:

• FactoryGirl/FactoryBot
• Fabrication.

RSpec

To activate FactoryDoctor use FDOC environment variable:

FDOC=1 rspec ...

Using with RSpecStamp

FactoryDoctor can be used with RSpec Stamp to automatically mark bad examples with custom tags. For example:

FDOC=1 FDOC_STAMP="fdoc:consider" rspec ...

After running the command above all potentially bad examples would be marked with the fdoc: :consider tag.

Minitest

To activate FactoryDoctor use FDOC environment variable:

FDOC=1 ruby ...

or use CLI option as shown below:

ruby ... --factory-doctor

The same option to force Factory Doctor to ignore specific examples is also available for Minitest. Just use fd_ignore inside your example:

# won't be reported as offense
it "is ignored" do
  fd_ignore

  @user.name = ""
  refute @user.valid?
end

Using with Minitest::Reporters

If you're using Minitest::Reporters in your project you have to explicitly declare it in your test helper file:

require 'minitest/reporters'
Minitest::Reporters.use! [YOUR_FAVORITE_REPORTERS]

NOTE: When you have minitest-reporters installed as a gem but not declared in your Gemfile make sure to always prepend your test run command with bundle exec (but we sure that you always do it). Otherwise, you'll get an error caused by Minitest plugin system, which scans all the entries in the $LOAD_PATH for any minitest/*_plugin.rb, thus initialization of minitest-reporters plugin which is available in that case doesn't happens correctly.

Configuration

The following configuration parameters are available (showing defaults):

TestProf::FactoryDoctor.configure do |config|
  # Which event to track within test example to consider them "DB-dirty"
  config.event = "sql.active_record"
  # Consider result "good" if the time in DB is less then the threshold
  config.threshold = 0.01
end

You can use the corresponding env variables as well: FDOC_EVENT and FDOC_THRESHOLD.