--- a/src/lib-index/Makefile.am	Thu Jan 28 17:53:41 2016 +0200
+++ b/src/lib-index/Makefile.am	Thu Jan 28 19:48:09 2016 +0200
@@ -61,6 +61,7 @@
         mailbox-log.h
 
 test_programs = \
+	test-mail-index-map \
 	test-mail-index-sync-ext \
 	test-mail-index-transaction-finish \
 	test-mail-index-transaction-update \
@@ -76,6 +77,10 @@
 
 test_deps = $(noinst_LTLIBRARIES) $(test_libs)
 
+test_mail_index_map_SOURCES = test-mail-index-map.c
+test_mail_index_map_LDADD = $(noinst_LTLIBRARIES) $(test_libs)
+test_mail_index_map_DEPENDENCIES = $(test_deps)
+
 test_mail_index_sync_ext_SOURCES = test-mail-index-sync-ext.c
 test_mail_index_sync_ext_LDADD = mail-index-sync-ext.lo $(test_libs)
 test_mail_index_sync_ext_DEPENDENCIES = $(test_deps)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/lib-index/test-mail-index-map.c	Thu Jan 28 19:48:09 2016 +0200
@@ -0,0 +1,57 @@
+/* Copyright (c) 2016 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "test-common.h"
+#include "mail-index-private.h"
+#include "mail-index-modseq.h"
+#include "mail-index-transaction-private.h"
+
+static void test_mail_index_map_lookup_seq_range_count(unsigned int messages_count)
+{
+	struct mail_index_record_map rec_map;
+	struct mail_index_map map;
+	uint32_t seq, first_uid, last_uid, first_seq, last_seq, max_uid;
+
+	memset(&map, 0, sizeof(map));
+	memset(&rec_map, 0, sizeof(rec_map));
+	map.rec_map = &rec_map;
+	map.hdr.messages_count = messages_count;
+	map.hdr.record_size = sizeof(struct mail_index_record);
+	rec_map.records_count = map.hdr.messages_count;
+	rec_map.records = i_new(struct mail_index_record, map.hdr.messages_count);
+
+	for (seq = 1; seq <= map.hdr.messages_count; seq++)
+		MAIL_INDEX_REC_AT_SEQ(&map, seq)->uid = seq*2;
+	max_uid = (seq-1)*2;
+	map.hdr.next_uid = max_uid + 1;
+
+	for (first_uid = 2; first_uid <= max_uid; first_uid++) {
+		for (last_uid = first_uid; last_uid <= max_uid; last_uid++) {
+			if (first_uid == last_uid && first_uid%2 != 0)
+				continue;
+			mail_index_map_lookup_seq_range(&map, first_uid, last_uid, &first_seq, &last_seq);
+			test_assert((first_uid+1)/2 == first_seq && last_uid/2 == last_seq);
+		}
+	}
+
+}
+
+static void test_mail_index_map_lookup_seq_range(void)
+{
+	unsigned int i;
+
+	test_begin("mail index map lookup seq range");
+	for (i = 1; i < 20; i++)
+		test_mail_index_map_lookup_seq_range_count(i);
+	test_end();
+}
+
+int main(void)
+{
+	static void (*test_functions[])(void) = {
+		test_mail_index_map_lookup_seq_range,
+		NULL
+	};
+	return test_run(test_functions);
+}