I'm thinking of a design roughly like:

1. within test.dart, run the dart test runner with --reporter=json
2. parse the JSON output
3. print useful data to STDOUT
4. at the end of the dart test runner invocation, print a JSON blob with a digest:
   a. all test files that were run
   b. all individual tests that were run, including the result
5. from recipe, POST these results back to Cocoon
6. if we are in a pre-submit context, comment the failures to the PR
7. if we are in a post-submit context, write the results to datastore