.mutant.yml

---
# Mutation testing (https://github.com/mbj/mutant). Run via `rake mutant`
# (the whole lib) or directly for one subject while iterating:
#
#   bundle exec mutant run 'SimpleCov::CLI::Tests*'
#
usage: opensource
includes:
  - lib
requires:
  - simplecov
  - simplecov/cli
  - simplecov/production
environment_variables:
  # The suite's own-coverage dogfooding instruments every mutation fork
  # and enforces 100% line coverage at exit, which would abort mutant's
  # partial runs. Mutation runs measure the tests, not the coverage.
  SIMPLECOV_NO_DOGFOOD: "1"
integration:
  name: rspec
matcher:
  subjects:
    - SimpleCov*
mutation:
  operators: full
  # Full operators produce infinite-loop mutations (flipped loop
  # conditions, dropped increments). The timeout converts them into
  # kills via the timeout coverage criterion below. It is set well above
  # any subject's honest test selection so a timeout means runaway
  # behavior, not a slow suite masking the result.
  timeout: 30.0
coverage_criteria:
  timeout: true
  # A mutation that takes the test process down with it is caught, the
  # same as one that fails an example. Without this a mutation whose
  # damage lands outside an example (in a hook, or on the way out of the
  # process) reads as surviving.
  process_abort: true