chefspec: Appears to be significantly slower with chef 13 than chef 12

I’m updating a number of our wrapper cookbooks and finding that the chefspec run is significantly slower with chef 13 than chef 12.

For example see https://travis-ci.org/ingenerator/chef-ingenerator-php/builds/262688704 - total job time of 9 minutes with chef 12, compared to 21 minutes with chef 13. Internally, rspec took 17 minutes 24 seconds on the chef 13 job, 8 minutes 11 seconds with chef 12.

I’m seeing the same discrepancy on all builds and on multiple cookbooks. The only difference between the two runs is the gemfile in use : one specifies chef 12 and the other specifies chef 13. Even the chef 12 build is about double what I was previously seeing with chefspec 5.4.0 and chef 12.

I have tried:

• verifying that I’m using SoloRunner rather than ServerRunner
• making sure that vendors etc are in a chefignore file
• setting config.server_runner_clear_cookbooks = false

Is this expected? Is there anything more I can do to reduce the runtime with Chef 13?