SimpleCov 0.18.3 at_exit bug

simplecov-ruby/simplecov#873

Issue

In a Rails application tested with RSpec (using the rspec-rails gem) the coverage report is not generated after the test suite has run.

Minimal reproduction

• Clone this repo & run bundle install
• Run bundle exec rspec
• Comment/uncomment the require "active_support/test_case" in spec/foo_spec.rb to observe the issue

Tracing the issue

When ActiveSupport::TestCase is required, by RSpec Rails for example:

https://github.com/rspec/rspec-rails/blob/e23efbb2cd6b40aaa8c6f33a36fe7ed4e724e2c7/spec/rspec/rails/matchers/redirect_to_spec.rb#L2

This ends up requiring minitest:

https://github.com/rails/rails/blob/c70112e74f4d2ef517f4036fe6e2888cc30fc952/activesupport/lib/active_support/test_case.rb#L4

Unfortunately Minitest is a dependency of ActiveSupport:

https://github.com/rails/rails/blob/c70112e74f4d2ef517f4036fe6e2888cc30fc952/activesupport/activesupport.gemspec#L38

By having defined Minitest, this means the SimpleCov at_exit hook will skip the 'at exit behaviour' hook:

at_exit do
  # Exit hook for Minitest defined in Minitest plugin
  next if defined?(Minitest)

  SimpleCov.at_exit_behavior
end

https://github.com/colszowka/simplecov/blob/a179ec6dc419c43bce472c2426f30f24cc49b42f/lib/simplecov/defaults.rb#L24-L29

PRs which introduced this behaviour:

• simplecov-ruby/simplecov#855
• simplecov-ruby/simplecov#756

Workaround

RSpec.configure do |config|
  config.after(:suite) { SimpleCov.at_exit_behavior }
end