When creating a new module with PDK, running unit tests gives the following message:
Deprecation Warnings: puppetlabs_spec_helper: defaults `mock_with` to `:mocha`. See https://github.com/puppetlabs/puppetlabs_spec_helper#mock_with to choose a sensible value for you
To switch to ":mocha" as mentioned, create a ".sync.yml" file in the module directory and add the following lines:
--- spec/spec_helper.rb: mock_with: ':rspec'
Then, run "pdk update" to apply the changes.