t/multi-mid.t: extra test for -convert highwater mark

This is derived from a real-world test case where I encounterd
multiple Message-IDs in a v1 inbox causing regen problems.

Fixes: eea47b676127bcdb ("convert: preserve highwater mark from v1 msgmap")

1 files changed, 1 insertions, 0 deletions

diff --git a/MANIFEST b/MANIFEST
index 3736c777..5eb5d53a 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -250,6 +250,7 @@ t/mime.t
 t/msg_iter.t
 t/msgmap.t
 t/msgtime.t
+t/multi-mid.t
 t/nntp.t
 t/nntpd-tls.t
 t/nntpd.t