update tests to be compatible w/ the SDK test runner

[pq]

In anticipation of running tests as part of the SDK build, we need to update them to run using the test discovery mechanism of our test runner.

Today:

dart --enable-asserts \
    --disable-analytics \
    test/all.dart

(Note the all.dart vs. discovery of _test.dart files.)

As a baby-step, updating bot.sh to use dart test seems good.

As part of this, we'll also want to convert

dart tool/checks/driver.dart

To be run as a test.

---

SDK migration readiness steps

• migrate bot.sh to invoke tests via dart test
  • tidy shared test setup #4405
• migrate tool/checks/driver.dart to a test run in the main test suite
  • migrate custom check verification to a test #4406

[srawlins]

In anticipation of running tests as part of the SDK build, we need to update them to run using the test discovery mechanism of our test runner.

What does this mean, to update each test? My understanding is that they should be fine.

[pq]

Tests currently depend on a mock IO sink being setup and rules registered. These things happen in all.dart typically. (This is a simplification and am happy to elaborate. Suffice it to say, many tests currently fail if some setup hasn't been done before they're invoked.)

[srawlins]

Oh wow I did not realize. Good catch.