diff --git a/openbsc/.gitignore b/openbsc/.gitignore
index 55f4a31..28fdcc8 100644
--- a/openbsc/.gitignore
+++ b/openbsc/.gitignore
@@ -80,6 +80,7 @@
 tests/subscr/subscr_test
 tests/oap/oap_test
 tests/gtphub/gtphub_test
+tests/mm_auth/mm_auth_test
 
 tests/atconfig
 tests/atlocal
diff --git a/openbsc/configure.ac b/openbsc/configure.ac
index 24dbc30..60601fe 100644
--- a/openbsc/configure.ac
+++ b/openbsc/configure.ac
@@ -216,6 +216,7 @@
     tests/subscr/Makefile
     tests/oap/Makefile
     tests/gtphub/Makefile
+    tests/mm_auth/Makefile
     doc/Makefile
     doc/examples/Makefile
     Makefile)
diff --git a/openbsc/include/openbsc/auth.h b/openbsc/include/openbsc/auth.h
index d41d141..90495bb 100644
--- a/openbsc/include/openbsc/auth.h
+++ b/openbsc/include/openbsc/auth.h
@@ -1,6 +1,8 @@
 #ifndef _AUTH_H
 #define _AUTH_H
 
+#include <osmocom/core/utils.h>
+
 struct gsm_auth_tuple;
 struct gsm_subscriber;
 
@@ -11,6 +13,12 @@
 	AUTH_DO_AUTH		= 3,	/* Only authentication, no ciphering */
 };
 
+extern const struct value_string auth_action_names[];
+static inline const char *auth_action_str(enum auth_action a)
+{
+	return get_value_string(auth_action_names, a);
+}
+
 int auth_get_tuple_for_subscr(struct gsm_auth_tuple *atuple,
                               struct gsm_subscriber *subscr, int key_seq);
 
diff --git a/openbsc/src/libmsc/auth.c b/openbsc/src/libmsc/auth.c
index 65a9b03..8512316 100644
--- a/openbsc/src/libmsc/auth.c
+++ b/openbsc/src/libmsc/auth.c
@@ -31,6 +31,15 @@
 
 #include <stdlib.h>
 
+const struct value_string auth_action_names[] = {
+#define AUTH_ACTION_STR(X) { X, #X }
+	{ -1, "(internal error)" }, /* soon to be fixed with an enum val */
+	AUTH_ACTION_STR(AUTH_NOT_AVAIL),
+	AUTH_ACTION_STR(AUTH_DO_AUTH_THEN_CIPH),
+	AUTH_ACTION_STR(AUTH_DO_CIPH),
+	AUTH_ACTION_STR(AUTH_DO_AUTH),
+#undef AUTH_ACTION_STR
+};
 
 static int
 _use_xor(struct gsm_auth_info *ainfo, struct gsm_auth_tuple *atuple)
diff --git a/openbsc/tests/Makefile.am b/openbsc/tests/Makefile.am
index 04b8e34..09298a3 100644
--- a/openbsc/tests/Makefile.am
+++ b/openbsc/tests/Makefile.am
@@ -1,4 +1,4 @@
-SUBDIRS = gsm0408 db channel mgcp gprs abis gbproxy trau subscr
+SUBDIRS = gsm0408 db channel mgcp gprs abis gbproxy trau subscr mm_auth
 
 if BUILD_NAT
 SUBDIRS += bsc-nat bsc-nat-trie
diff --git a/openbsc/tests/mm_auth/Makefile.am b/openbsc/tests/mm_auth/Makefile.am
new file mode 100644
index 0000000..516df00
--- /dev/null
+++ b/openbsc/tests/mm_auth/Makefile.am
@@ -0,0 +1,21 @@
+AM_CPPFLAGS = $(all_includes) -I$(top_srcdir)/include
+AM_CFLAGS=-Wall \
+	  $(LIBOSMOCORE_CFLAGS) \
+	  $(LIBOSMOGSM_CFLAGS) \
+	  $(LIBCRYPTO_CFLAGS)
+
+noinst_PROGRAMS = mm_auth_test
+
+EXTRA_DIST = mm_auth_test.ok
+
+mm_auth_test_SOURCES = mm_auth_test.c
+
+mm_auth_test_LDFLAGS = \
+	-Wl,--wrap=db_get_authinfo_for_subscr \
+	-Wl,--wrap=db_get_lastauthtuple_for_subscr \
+	-Wl,--wrap=db_sync_lastauthtuple_for_subscr
+
+mm_auth_test_LDADD = $(top_builddir)/src/libmsc/libmsc.a \
+		     $(top_builddir)/src/libcommon/libcommon.a \
+		     $(LIBOSMOCORE_LIBS) \
+		     $(LIBOSMOGSM_LIBS)
diff --git a/openbsc/tests/mm_auth/mm_auth_test.c b/openbsc/tests/mm_auth/mm_auth_test.c
new file mode 100644
index 0000000..d8e4475
--- /dev/null
+++ b/openbsc/tests/mm_auth/mm_auth_test.c
@@ -0,0 +1,119 @@
+#include <stdbool.h>
+
+#include <osmocom/core/application.h>
+#include <osmocom/core/logging.h>
+
+#include <openbsc/debug.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/gsm_subscriber.h>
+#include <openbsc/auth.h>
+
+/* override, requires '-Wl,--wrap=db_get_authinfo_for_subscr' */
+int __real_db_get_authinfo_for_subscr(struct gsm_auth_info *ainfo,
+				      struct gsm_subscriber *subscr);
+
+int test_get_authinfo_rc = 0;
+struct gsm_auth_info test_auth_info = {0};
+struct gsm_auth_info default_auth_info = {
+	.auth_algo = AUTH_ALGO_COMP128v1,
+	.a3a8_ki_len = 16,
+	.a3a8_ki = { 0 }
+};
+
+int __wrap_db_get_authinfo_for_subscr(struct gsm_auth_info *ainfo,
+				      struct gsm_subscriber *subscr)
+{
+	*ainfo = test_auth_info;
+	printf("wrapped: db_get_authinfo_for_subscr(): rc = %d\n", test_get_authinfo_rc);
+	return test_get_authinfo_rc;
+}
+
+/* override, requires '-Wl,--wrap=db_get_lastauthtuple_for_subscr' */
+int __real_db_get_lastauthtuple_for_subscr(struct gsm_auth_tuple *atuple,
+					   struct gsm_subscriber *subscr);
+
+int test_get_lastauthtuple_rc = 0;
+struct gsm_auth_tuple test_last_auth_tuple = { 0 };
+struct gsm_auth_tuple default_auth_tuple = { 0 };
+
+int __wrap_db_get_lastauthtuple_for_subscr(struct gsm_auth_tuple *atuple,
+					   struct gsm_subscriber *subscr)
+{
+	*atuple = test_last_auth_tuple;
+	printf("wrapped: db_get_lastauthtuple_for_subscr(): rc = %d\n", test_get_lastauthtuple_rc);
+	return test_get_lastauthtuple_rc;
+}
+
+/* override, requires '-Wl,--wrap=db_sync_lastauthtuple_for_subscr' */
+int __real_db_sync_lastauthtuple_for_subscr(struct gsm_auth_tuple *atuple,
+					    struct gsm_subscriber *subscr);
+int test_sync_lastauthtuple_rc = 0;
+int __wrap_db_sync_lastauthtuple_for_subscr(struct gsm_auth_tuple *atuple,
+					    struct gsm_subscriber *subscr)
+{
+	test_last_auth_tuple = *atuple;
+	printf("wrapped: db_sync_lastauthtuple_for_subscr(): rc = %d\n", test_sync_lastauthtuple_rc);
+	return test_sync_lastauthtuple_rc;
+}
+
+int auth_get_tuple_for_subscr_verbose(struct gsm_auth_tuple *atuple,
+				      struct gsm_subscriber *subscr,
+				      int key_seq)
+{
+	int auth_action;
+	auth_action = auth_get_tuple_for_subscr(atuple, subscr, key_seq);
+	printf("auth_get_tuple_for_subscr(key_seq=%d) --> auth_action == %s\n",
+	       key_seq, auth_action_str(auth_action));
+	return auth_action;
+}
+
+/* override libssl RAND_bytes() to get testable crypto results */
+int RAND_bytes(uint8_t *rand, int len)
+{
+	memset(rand, 23, len);
+	return 1;
+}
+
+static void test_error()
+{
+	int auth_action;
+
+	struct gsm_auth_tuple atuple = {0};
+	struct gsm_subscriber subscr = {0};
+	int key_seq = 0;
+
+	printf("\n* test_error()\n");
+
+	/* any error (except -ENOENT) */
+	test_get_authinfo_rc = -EIO;
+	auth_action = auth_get_tuple_for_subscr_verbose(&atuple, &subscr,
+							key_seq);
+	OSMO_ASSERT(auth_action == -1);
+}
+
+static void test_auth_not_avail()
+{
+	int auth_action;
+
+	struct gsm_auth_tuple atuple = {0};
+	struct gsm_subscriber subscr = {0};
+	int key_seq = 0;
+
+	printf("\n* test_auth_not_avail()\n");
+
+	/* no entry */
+	test_get_authinfo_rc = -ENOENT;
+	auth_action = auth_get_tuple_for_subscr_verbose(&atuple, &subscr,
+							key_seq);
+	OSMO_ASSERT(auth_action == AUTH_NOT_AVAIL);
+}
+
+int main(void)
+{
+	osmo_init_logging(&log_info);
+	log_set_log_level(osmo_stderr_target, LOGL_INFO);
+
+	test_error();
+	test_auth_not_avail();
+	return 0;
+}
diff --git a/openbsc/tests/mm_auth/mm_auth_test.ok b/openbsc/tests/mm_auth/mm_auth_test.ok
new file mode 100644
index 0000000..5efb3de
--- /dev/null
+++ b/openbsc/tests/mm_auth/mm_auth_test.ok
@@ -0,0 +1,8 @@
+
+* test_error()
+wrapped: db_get_authinfo_for_subscr(): rc = -5
+auth_get_tuple_for_subscr(key_seq=0) --> auth_action == (internal error)
+
+* test_auth_not_avail()
+wrapped: db_get_authinfo_for_subscr(): rc = -2
+auth_get_tuple_for_subscr(key_seq=0) --> auth_action == AUTH_NOT_AVAIL
diff --git a/openbsc/tests/testsuite.at b/openbsc/tests/testsuite.at
index 6a1c77f..dab9568 100644
--- a/openbsc/tests/testsuite.at
+++ b/openbsc/tests/testsuite.at
@@ -117,3 +117,10 @@
 cat $abs_srcdir/gtphub/gtphub_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/gtphub/gtphub_test], [], [expout], [ignore])
 AT_CLEANUP
+
+AT_SETUP([mm_auth])
+AT_KEYWORDS([mm_auth])
+cat $abs_srcdir/mm_auth/mm_auth_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/mm_auth/mm_auth_test], [], [expout], [ignore])
+AT_CLEANUP
+