t: add msed tests

t/4000-msed.t

@@ -0,0 +1,35 @@
+#!/bin/sh -e
+cd ${0%/*}
+. ./lib.sh
+plan 6
+
+rm -rf test.dir
+mkdir test.dir
+(
+cd test.dir
+
+mkdir -p "inbox/cur"
+
+cat <<! | mmime >"inbox/cur/1:2,"
+From: Rajwinder Kaur <rajwinder@example.com>
+Subject: Hello
+Date: Thu, 30 Mar 2017 15:42:05 +0200
+Message-Id: <EOH1F3NUOY.2KBVMHSBFATNY@example.org>
+
+body
+!
+
+cat <<! >seq
+inbox/cur/1:2,
+!
+
+export MAILSEQ=seq
+
+check 'append new' 'msed "/foobar/a/value/" 1 | grep "Foobar: value"'
+check 'append existing' 'msed "/subject/a/world/" 1 | grep -v "world"'
+check 'append multiple' 'msed "/foo/a/catch/;/bar/a/catch/" 1 | grep -c catch | grep -qx 2'
+check 'change' 'msed "/subject/c/world/" 1 | grep "Subject: world"'
+check 'delete' 'msed "/message-id/d" 1 | grep -v "Message-Id"'
+check 'substitute' 'msed "/subject/s/\(Hello\)/\1 World/" 1 | grep "^Subject: Hello World$"'
+
+)