The numbers presented in the test result don't seem to add up:

13 tests were completed in 274s with 12 passed, 0 failed and 0 skipped.

I don't understand how the number of completed tests is formed. But I would assume it to be the sum of passed + failed.
In fact, in the given test suite, there were 12 tests (test(…);) included. So I would have expected "12 tests were completed …".

This is the originating test results file of reporter: "flutter-json":
test-results.json