* lisp/erc/erc-networks.el (erc-networks--determine): Return the
so-called "given" ID from a non-nil `:id' keyword arg passed to `erc'
or `erc-tls'.
(erc-networks--allow-unknown-network): Add internal variable to
allow IRC session to continue despite the network being unknown.
(erc-networks--set-name): Tell the user about falling back to a given
ID when the network can't be determined.  When that's so, end the
session by destroying the connection unless
`erc-networks--allow-unknown-network' is enabled.  (Bug#59976.)
(erc-networks--ensure-announced): Include the fallback announced
server name in the error message.
* test/lisp/erc/erc-networks-tests.el (erc-networks--set-name): Add
dummy server process and don't expect an error to be signaled.
* test/lisp/erc/erc-scenarios-misc.el
(erc-scenarios-networks-announced-missing): Don't expect an error to
be signaled.
* test/lisp/erc/resources/networks/announced-missing/foonet.eld:
Remove "mode" match pattern.

* test/lisp/erc/erc-scenarios-base-association-nick.el: New file.
* test/lisp/erc/erc-scenarios-base-association-samenet.el: New file.
* test/lisp/erc/erc-scenarios-base-association.el: New file.
* test/lisp/erc/erc-scenarios-base-compat-rename-bouncer.el: New file.
* test/lisp/erc/erc-scenarios-base-misc-regressions.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-bouncer-id.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-bouncer-recon-base.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-bouncer-recon-both.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-bouncer-recon-id.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-bouncer.el: New file.
* test/lisp/erc/erc-scenarios-base-netid-samenet.el: New file.
* test/lisp/erc/erc-scenarios-base-reconnect.el: New file.
* test/lisp/erc/erc-scenarios-base-renick.el: New file.
* test/lisp/erc/erc-scenarios-base-reuse-buffers.el: New file.
* test/lisp/erc/erc-scenarios-base-unstable.el: New file.
* test/lisp/erc/erc-scenarios-base-upstream-recon-soju.el: New file.
* test/lisp/erc/erc-scenarios-base-upstream-recon-znc.el: New file.
* test/lisp/erc/erc-scenarios-misc.el: New file.
* test/lisp/erc/erc-scenarios-services-misc.el: New file.
* test/lisp/erc/resources/base/assoc/bouncer-history/barnet.eld: New file.
* test/lisp/erc/resources/base/assoc/bouncer-history/foonet.eld: New file.
* test/lisp/erc/resources/base/assoc/bumped/again.eld: New file.
* test/lisp/erc/resources/base/assoc/bumped/foisted.eld: New file.
* test/lisp/erc/resources/base/assoc/bumped/refoisted.eld: New file.
* test/lisp/erc/resources/base/assoc/bumped/renicked.eld: New file.
* test/lisp/erc/resources/base/assoc/multi-net/barnet.eld: New file.
* test/lisp/erc/resources/base/assoc/multi-net/foonet.eld: New file.
* test/lisp/erc/resources/base/assoc/reconplay/again.eld: New file.
* test/lisp/erc/resources/base/assoc/reconplay/foonet.eld: New file.
* test/lisp/erc/resources/base/assoc/samenet/chester.eld: New file.
* test/lisp/erc/resources/base/assoc/samenet/tester.eld: New file.
* test/lisp/erc/resources/base/assoc/samenet/tester2.eld: New file.
* test/lisp/erc/resources/base/channel-buffer-revival/foonet.eld: New file.
* test/lisp/erc/resources/base/flood/soju.eld: New file.
* test/lisp/erc/resources/base/gapless-connect/barnet.eld: New file.
* test/lisp/erc/resources/base/gapless-connect/foonet.eld: New file.
* test/lisp/erc/resources/base/gapless-connect/pass-stub.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/barnet-again.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/barnet-drop.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/barnet.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/foonet-again.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/foonet-drop.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/foonet.eld: New file.
* test/lisp/erc/resources/base/netid/bouncer/stub-again.eld: New file.
* test/lisp/erc/resources/base/netid/samenet/chester.eld: New file.
* test/lisp/erc/resources/base/netid/samenet/tester.eld: New file.
* test/lisp/erc/resources/base/reconnect/aborted-dupe.eld: New file.
* test/lisp/erc/resources/base/reconnect/aborted.eld: New file.
* test/lisp/erc/resources/base/reconnect/options-again.eld: New file.
* test/lisp/erc/resources/base/reconnect/options.eld: New file.
* test/lisp/erc/resources/base/reconnect/timer-last.eld: New file.
* test/lisp/erc/resources/base/reconnect/timer.eld: New file.
* test/lisp/erc/resources/base/renick/queries/bouncer-barnet.eld: New file.
* test/lisp/erc/resources/base/renick/queries/bouncer-foonet.eld: New file.
* test/lisp/erc/resources/base/renick/queries/solo.eld: New file.
* test/lisp/erc/resources/base/renick/self/auto.eld: New file.
* test/lisp/erc/resources/base/renick/self/manual.eld: New file.
* test/lisp/erc/resources/base/renick/self/qual-chester.eld: New file.
* test/lisp/erc/resources/base/renick/self/qual-tester.eld: New file.
* test/lisp/erc/resources/base/reuse-buffers/server/barnet.eld: New file.
* test/lisp/erc/resources/base/reuse-buffers/server/foonet.eld: New file.
* test/lisp/erc/resources/base/upstream-reconnect/soju-barnet.eld: New file.
* test/lisp/erc/resources/base/upstream-reconnect/soju-foonet.eld: New file.
* test/lisp/erc/resources/base/upstream-reconnect/znc-barnet.eld: New file.
* test/lisp/erc/resources/base/upstream-reconnect/znc-foonet.eld: New file.
* test/lisp/erc/resources/erc-scenarios-common.el: New file.
* test/lisp/erc/resources/networks/announced-missing/foonet.eld: New file.
* test/lisp/erc/resources/services/password/libera.eld: New file.

Add test cases for locking down fundamental client behavior, much of
it involving the relationship between buffers and connections.  Also
add accompanying resources subdir containing canned dialog scripts and
common code needed by various tests.  For test cases demoing the
problematic behavior originally described in the initial report, see
update #4 on the bug tracker thread for bug#48598.  Most reside in a
file named test/lisp/erc/erc-scenarios-48598.el introduced by the
patch "Add user-oriented test scenarios for ERC".