If you’re running tests for your iOS code base on some kind of Continuous Integration, you usually have to generate a JUnit file to report the test results, including error information, to your CI system. Until now, the easiest solution was to use the amazing xcpretty, which parses the xcodebuild output and converts it to something more readable, additionally to generating the JUnit report.

Since there were some difficulties with the new Xcode 8, Peter Steinberger and me had the idea to parse the test results the same way Xcode server does it: using the Xcode plist logs. 

trainer is a simple standalone tool (that also contains a fastlane plugin), which does exactly that: Convert the plist files to JUnit reports.

By using trainer, the Twitter iOS code base now generates JUnit reports 10 times faster.

To start using trainer, just add the following to your Fastfile:

lane :test do
  scan(scheme: "ThemojiUITests", 
       output_types: "", 
       fail_build: false)

  trainer(output_directory: ".")
end

By combining trainer with danger, you can automatically show the failed tests right in your pull request, without having to open the actual output.

For more information about when to use trainer, check out the full blog article on PSPDFKit.