free_mutant/docs/mutant-rspec.md

mutant-rspec

The integration into rspec.

Install mutant-rspec and use the --use rspec switch in your mutant command line.

bundle exec mutant --include lib --require 'your_code' --use rspec -- 'YourCode*'

Examples

cd virtus
# Run mutant on virtus namespace
bundle exec mutant --include lib --require virtus --use rspec Virtus*
# Run mutant on specific virtus class
bundle exec mutant --include lib --require virtus --use rspec Virtus::Attribute
# Run mutant on specific virtus class method
bundle exec mutant --include lib --require virtus --use rspec Virtus::Attribute.build
# Run mutant on specific virtus instance method
bundle exec mutant --include lib --require virtus --use rspec Virtus::Attribute#type

Test-Selection

Mutation testing is slow. The key to making it fast is selecting the correct set of tests to run. Mutant currently supports the following built-in strategy for selecting tests/specs:

Mutant uses the "longest rspec example group descriptions prefix match" to select the tests to run.

Example for a subject like Foo::Bar#baz it will run all example groups with description prefixes in Foo::Bar#baz, Foo::Bar and Foo. The order is important, so if mutant finds example groups in the current prefix level, these example groups must kill the mutation.

Rails

To mutation test Rails models with rspec, comment out require 'rspec/autorun' from your spec_helper.rb file. Having done so you should be able to use commands like the following:

RAILS_ENV=test bundle exec mutant -r ./config/environment --use rspec User

Passing in RSpec Options

NOTE: Experimental

You can control some aspects of RSpec using the SPEC_OPTS environment variable as usual. If you want mutant to only pay attention to specs in a certain directory, you can run

SPEC_OPTS="--pattern spec/subdir_only/**/*_spec.rb" bundle exec mutant --use rspec SomeClass