factory_sloth is too lazy to write to the database.
It finds unnecessary factory_bot create calls and replaces them with less laborious build or build_stubbed calls to speed up your test suite.
bundle add factory_sloth or gem install factory_sloth.
Output of factory_sloth --help:
Usage: factory_sloth [path1, path2, ...] [options]
Examples:
factory_sloth # run for all specs
factory_sloth spec/models
factory_sloth spec/foo_spec.rb spec/bar_spec.rb
Options:
-f, --force Ignore ./.factory_sloth_done
-l, --lint Dont fix, just list bad create calls
-V, --verbose Verbose output, useful for debugging
-v, --version Show gem version
-h, --help Show this help
factory_sloth runs the changed specs to see if they still work. This takes a while for all possible changes - usually multiple times as long as the specs would normally take to run! For this reason, the gem creates a .factory_sloth_done file. This is a list of specs that have already been processed. It makes it possible to interrupt the program and continue later. You can delete this file to start over or ignore it with -f.
While running, factory_sloth produces output like this:
🟡 spec/features/sign_up_spec.rb: 2 create calls found, 0 replaced
⚪️ spec/lib/string_ext_spec.rb: 0 create calls found, 0 replaced
spec/models/user_spec.rb:3:2: create replaced with build
expect(create(:user)).not_to be_nil
^^^^^^
spec/models/user_spec.rb:4:2: create_list replaced with build_list
expect(create_list(:user, 2).count).to eq 2
^^^^^^^^^^^
🟢 spec/models/user_spec.rb: 3 create calls found, 2 replaced
spec/weird_dir/crazy_spec.rb:8:4: create replaced with build_stubbed
expect(create(:user)).not_to be_nil
^^^^^^
🔴 spec/weird_dir/crazy_spec.rb: 33 create calls found, 0 replaced (conflict)
Scanned 4 files, found 2 unnecessary create calls across 1 files and 1 broken specs
The conflict case is rare. It only happens if individual examples were green after changing them, but at least one example failed when evaluating the whole file after all changes. This probably means that some other example was red even before making changes, or that something else is wrong with this spec file, e.g. some examples depend on other examples' side effects.
factory_sloth only works with RSpec so far. It also works best with unit tests such as model specs. It generates false positives in cases where create calls are done but only the absence of any effect is tested, e.g.:
user = create(:user)
User.delete_all
expect(User.count).to eq 0This test will still pass if user is never inserted into the database in the first place, leading factory_sloth to believe that build suffices here. However, this change makes the test no longer assert the same thing and reduces coverage. Magic comments can be used to prevent factory_sloth from making such changes. factory_sloth will not touch lines with inline # sloth:disable comments, or sections framed in # sloth:disable / # sloth:enable comments. Another option is to write the test in a different (and arguably more assertive) way, e.g.:
expect { User.delete_all }.to change { User.count }.from(1).to(0)If you have a good idea about how to detect such cases automatically, let me know :)
After checking out the repo, run bin/setup to install dependencies. Then, run rake to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.
Bug reports and pull requests are welcome on GitHub at https://github.com/jaynetics/factory_sloth.
The gem is available as open source under the terms of the MIT License.
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