test: fix flaky test-http-highwatermark
The current version of the test is dependent on the requests coming in before the data is successfully sent & read. Make write
size much larger and delay the read
on the other side a bit to get rid of the flakiness.
Fixes: https://github.com/nodejs/node/issues/17857
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines
Affected core subsystem(s)
test