Slightly changing my original proposal, how's

```
rspec_err = StringIO.new

 # We assume the only interesting output from a failed rspec run is present on stderr.
killed = !::RSpec::Core::Runner.run(command_line_arguments, nil, rspec_err).zero?

rspec_err.rewind

# Failures in noop may indicate a broken test suite, but they can also be an indication
# mutant has altered the runtime environment in a subtle way and has tickled an odd bug.
# Therefore we surface the output of any noop rspec failures.
case mutation
when Mutant::Mutation::Neutral::Noop
  if killed
    puts "#{mutation.class} test failed."
    puts 'RSpec stderr:'
    puts rspec_err.read
  end
end

killed
```

for a first pass?

Alternately, I could go ahead and add `Mutant::Mutation#should_survive?` to the `Mutation` base classes, set it to `true` in `Mutant::Mutation::Neutral::Noop`, and this code would reduce to:

```
rspec_err = StringIO.new

 # We assume the only interesting output from a failed rspec run is present on stderr.
killed = !::RSpec::Core::Runner.run(command_line_arguments, nil, rspec_err).zero?

if killed and mutation.should_survive?
  puts "#{mutation.class} test failed."
  puts 'RSpec stderr:'
  puts rspec_err.read
end

killed
```