+is($uri->uid(undef), undef, 'uid can be clobbered');
+is($$uri, 'imap://0/mmm;UIDVALIDITY=4', 'uid dropped');
+
+$uri->auth('ANONYMOUS');
+is($$uri, 'imap://;AUTH=ANONYMOUS@0/mmm;UIDVALIDITY=4', 'AUTH= set');
+is($uri->user, undef, 'user is undef w/ AUTH=');
+is($uri->password, undef, 'password is undef w/ AUTH=');
+
+$uri->user('foo');
+is($$uri, 'imap://foo;AUTH=ANONYMOUS@0/mmm;UIDVALIDITY=4', 'user set w/AUTH');
+is($uri->password, undef, 'password is undef w/ AUTH= & user');
+$uri->auth(undef);
+is($$uri, 'imap://foo@0/mmm;UIDVALIDITY=4', 'user remains set w/o auth');
+is($uri->password, undef, 'password is undef w/ user only');
+
+$uri->user('bar');
+is($$uri, 'imap://bar@0/mmm;UIDVALIDITY=4', 'user set w/o AUTH');
+$uri->auth('NTML');
+is($$uri, 'imap://bar;AUTH=NTML@0/mmm;UIDVALIDITY=4', 'auth set w/user');
+$uri->auth(undef);
+$uri->user(undef);
+is($$uri, 'imap://0/mmm;UIDVALIDITY=4', 'auth and user both cleared');
+is($uri->user, undef, 'user is undef');
+is($uri->auth, undef, 'auth is undef');
+is($uri->password, undef, 'password is undef');
+$uri = PublicInbox::URIimap->new('imap://[::1]:36281/');
+my $cred = bless { username => $uri->user, password => $uri->password };
+is($cred->{username}, undef, 'user is undef in array context');
+is($cred->{password}, undef, 'password is undef in array context');
+