Test servers may be obscuring bugs

[alxndrsn]

Bug Description

While investigating #4103, I noticed that node:http.createServer((req, res) => ... is used in various places in the test suite.

Without the option joinDuplicateHeaders, these servers behave as follows:

If set to true, this option allows joining the field line values of multiple headers in a request with a comma (, ) instead of discarding the duplicates. For more information, refer to message.headers. Default: false.

• https://nodejs.org/api/http.html#httpcreateserveroptions-requestlistener

This is very helpful if trying to implement a well-behaved server, but maybe less helpful if trying to test client behaviour.

Reproducible By

Expected Behavior

joinDuplicateHeaders should be set to true for every invocation of createServer() in tests.

Logs & Screenshots

Environment

Additional context