test: Add a test for HTML email with inline images

Currently this test passes in Emacs 23 but fails in Emacs 24 (at least
on some Linux distributions).

test/emacs

@@ -749,4 +749,38 @@ counter=$(test_emacs \
 )
 test_expect_equal "$counter" 2
 
+
+test_begin_subtest "Rendering HTML mail with images"
+add_message '[subject]="HTML mail with images"' \
+    '[content-type]="multipart/related; boundary=abcd"' \
+    '[body]="--abcd
+Content-Type: text/html
+
+<img src="cid:330@goomoji.gmail">
+
+--abcd
+Content-Type: image/gif
+Content-Transfer-Encoding: base64
+Content-ID: <330@goomoji.gmail>
+
+R0lGODlhDAAMAKIFAF5LAP/zxAAAANyuAP/gaP///wAAAAAAACH5BAEAAAUALAAAAAAMAAwAAAMl
+WLPcGjDKFYi9lxKBOaGcF35DhWHamZUW0K4mAbiwWtuf0uxFAgA7
+--abcd--"'
+test_emacs "(notmuch-show \"id:${gen_msg_id}\")
+	    (test-output)"
+# Normalize output for Emacs 23 and Emacs 24
+sed -i 's/\[cid\]/*/' OUTPUT
+cat <<EOF >EXPECTED
+Notmuch Test Suite <test_suite@notmuchmail.org> (2001-01-05) (inbox)
+Subject: HTML mail with images
+To: Notmuch Test Suite <test_suite@notmuchmail.org>
+Date: Fri, 05 Jan 2001 15:43:57 +0000
+
+[ multipart/related ]
+[ text/html ]
+*
+EOF
+test_expect_equal_file OUTPUT EXPECTED
+
+
 test_done