After upgrading my Rails app's JRuby version from JRuby 1.7.27 to JRuby 9.1.13 I noticed a drop in coverage levels in my code base from 100% to roughly 94%.

I'm using the SimpleCov Gem to output the rspec coverage but it uses Ruby's underlying Coverage module to get the actual coverage numbers.
(rspec 3.6 and simplecov 0.15)

Environment

JRuby 9.1.13

• rspec 3.6 and simplecov 0.15

• Rails

Expected Behavior

Behavior prior to upgrade

Behavior in ruby 2.4.1 using (rbenv)

Actual Behavior

Behavior post upgrade to JRuby 9.1.13

Here's a screen shot of a happy test to prove that testing does indeed work in my JRuby 9.1.13 setup (removed the instance variable)

As seen in the screen shots of the simple test above, coverage is incorrectly skipped in jruby9000 in certain cases (instance variable in a boolean condition in the above case)

I can post more examples if necessary for debugging.

Am I just missing some special flag when calling rspec, or is there something bigger going on here?
I've run with --dev, --debug, and -Xcli.debug=true