simplecov を JRuby 9.1.9.0 で実行した際に以下のようなエラーが出た場合は、JRuby 9.1.9.0 のリグレッションが原因。
Finished in 5.72 seconds (files took 3.22 seconds to load) 199 examples, 0 failures NoMethodError: undefined method `status' for #<Array:0x64206cad> block in result at (erb):15 each at org/jruby/RubyArray.java:1734 each_with_index at org/jruby/RubyEnumerable.java:1067 <eval> at (erb):14 eval at org/jruby/RubyKernel.java:1000 result at /home/travis/.rvm/rubies/jruby-9.1.9.0/lib/ruby/stdlib/erb.rb:864 formatted_source_file at /home/travis/.rvm/gems/jruby-9.1.9.0/gems/simplecov-html-0.10.0/lib/simplecov-html.rb:56 block in result at (erb):36 each at org/jruby/RubyArray.java:1734 <eval> at (erb):35 eval at org/jruby/RubyKernel.java:1000 result at /home/travis/.rvm/rubies/jruby-9.1.9.0/lib/ruby/stdlib/erb.rb:864 block in format at /home/travis/.rvm/gems/jruby-9.1.9.0/gems/simplecov-html-0.10.0/lib/simplecov-html.rb:23 open at org/jruby/RubyIO.java:1156 format at /home/travis/.rvm/gems/jruby-9.1.9.0/gems/simplecov-html-0.10.0/lib/simplecov-html.rb:22 format! at /home/travis/.rvm/gems/jruby-9.1.9.0/gems/simplecov-0.13.0/lib/simplecov/result.rb:47 block in at_exit at /home/travis/.rvm/gems/jruby-9.1.9.0/gems/simplecov-0.13.0/lib/simplecov/configuration.rb:172 block in (root) at /home/travis/.rvm/gems/jruby-9.1.9.0/gems/simplecov-0.13.0/lib/simplecov/defaults.rb:67
simplecov が依存している simplecov-html のバージョンをバグフィックス版の 0.10.1 にアップグレードすることで解決する。