Use PARALLEL_TESTS_EXECUTABLE environmental variable if it's provided

[hsbt]

👋 Thank you for maintaining turbo_tests.

I would like to use turbo_tests on ruby/ruby same as rubygems/rubygems for testing bundler. see ruby/ruby#12250.

We used parallel_tests because turbo_tests didn't support ENV["PARALLEL_TESTS_EXECUTABLE"] for custom executable on parallel_tests. I added new condition for that around command_name.

How about this? Thank you for reading this.

[deivid-rodriguez]

Should this be RSPEC_EXECUTABLE or something like that?

My understanding is that PARALLEL_TESTS_EXECUTABLE is a parallel_tests thing that helps in environments where ruby needs to be run differently (like in ruby-core test setup), but the way it's implemented here it's replacing rspec, so the consumer of this library will need to include some command line to help running rspec in the ENV, right?

[hsbt]

Should this be RSPEC_EXECUTABLE or something like that?

I have no strong opinion about that. RSPEC_EXECUTABLE is okay to me.

My understanding is that PARALLEL_TESTS_EXECUTABLE is a parallel_tests thing that helps in environments where ruby needs to be run differently (like in ruby-core test setup), but the way it's implemented here it's replacing rspec, so the consumer of this library will need to include some command line to help running rspec in the ENV, right?

Yes. ruby-core need to use miniruby for testing bundler before ruby installation. The current implementation forces to use rspec by gem install or bundle install.