in src/_Private/Progress.hack [36:48]
public async function testStartingAsync(
string $test_method,
?(arraykey, Container<mixed>) $data_provider_row,
): Awaitable<void> {
$ev = new HackTest\TestStartingProgressEvent(
$this->path,
$this->class,
$test_method,
$data_provider_row,
);
$cb = $this->callback;
await $cb($ev);
}