`TestEventSender` should not be Clone so we don't end up with multiple
copies of the same writer FD. This is probably not the cause of the test
channel lockups, but it's a lot easier to reason about.
The tests would deadlock if we tried to write the sync marker into a
pipe that was full because one test streamed just enough data to fill
the pipe, so when we went to actually write the sync marker we blocked
when nobody was reading.
We use a two-phase lock for sync markers now: one to indicate "ready to
sync" and the second to indicate that the sync bytes have been received.
Some `deno_std` tests were failing to print output that was resolved
after the last test finished. In addition, output printed before tests
began would sometimes appear above the "running X tests ..." line, and
sometimes below it depending on timing.
We now guarantee that all output is flushed before and after tests run,
making the output consistent.
Pre-test and post-test output are captured in `------ pre-test output
------` and `------ post-test output ------` blocks to differentiate
them from the regular output blocks.
Here's an example of a test (that is much noisier than normal, but an
example of what the output will look like):
```
Check ./load_unload.ts
------- pre-test output -------
load
----- output end -----
running 1 test from ./load_unload.ts
test ...
------- output -------
test
----- output end -----
test ... ok ([WILDCARD])
------- post-test output -------
unload
----- output end -----
```
Gets us closer to solving #20707.
Rewrites the `TestEventSender`:
- Allow for explicit creation of multiple streams. This will allow for
one-std{out,err}-per-worker
- All test events are received along with a worker ID, allowing for
eventual, proper parallel threading of test events.
In theory this should open up proper interleaving of test output,
however that is left for a future PR.
I had some plans for a better performing synchronization primitive, but
the inter-thread communication is tricky. This does, however, speed up
the processing of large numbers of tests 15-25% (possibly even more on
100,000+).
Before
```
ok | 1000 passed | 0 failed (32ms)
ok | 10000 passed | 0 failed (276ms)
```
After
```
ok | 1000 passed | 0 failed (25ms)
ok | 10000 passed | 0 failed (230ms)
```
