diff --git a/tests/sys/sound/sndstat.c b/tests/sys/sound/sndstat.c
--- a/tests/sys/sound/sndstat.c
+++ b/tests/sys/sound/sndstat.c
@@ -30,8 +30,9 @@
 
 #include <sys/param.h>
 #include <sys/linker.h>
-#include <sys/sndstat.h>
 #include <sys/nv.h>
+#include <sys/sndstat.h>
+#include <sys/soundcard.h>
 
 #include <atf-c.h>
 #include <errno.h>
@@ -46,26 +47,15 @@
 		atf_tc_skip("snd_dummy.ko not found");
 }
 
-ATF_TC(sndstat_nv);
-ATF_TC_HEAD(sndstat_nv, tc)
-{
-	atf_tc_set_md_var(tc, "descr", "/dev/sndstat nvlist test");
-}
-
-ATF_TC_BODY(sndstat_nv, tc)
+static void
+read_all(int fd)
 {
 	nvlist_t *nvl;
 	const nvlist_t * const *di;
 	const nvlist_t * const *cdi;
 	struct sndstioc_nv_arg arg;
 	size_t nitems, nchans, i, j;
-	int fd, rc;
-	int pchan, rchan;
-
-	load_dummy();
-
-	if ((fd = open("/dev/sndstat", O_RDONLY)) < 0)
-		atf_tc_skip("/dev/sndstat not found, load sound(4)");
+	int rc, pchan, rchan;
 
 	rc = ioctl(fd, SNDSTIOC_REFRESH_DEVS, NULL);
 	ATF_REQUIRE_EQ(rc, 0);
@@ -135,7 +125,6 @@
 		}
 #undef NV
 
-		/* XXX Do we need to skip the TC? userdevs won't have this list */
 		if (!nvlist_exists(di[i], SNDST_DSPS_PROVIDER_INFO))
 			continue;
 
@@ -203,12 +192,92 @@
 
 	free(arg.buf);
 	nvlist_destroy(nvl);
+}
+
+ATF_TC(sndstat_nv);
+ATF_TC_HEAD(sndstat_nv, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "/dev/sndstat nvlist test");
+}
+
+ATF_TC_BODY(sndstat_nv, tc)
+{
+	int fd;
+
+	load_dummy();
+
+	if ((fd = open("/dev/sndstat", O_RDONLY)) < 0)
+		atf_tc_skip("/dev/sndstat not found, load sound(4)");
+	read_all(fd);
+	close(fd);
+}
+
+ATF_TC(sndstat_udev);
+ATF_TC_HEAD(sndstat_udev, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "/dev/sndstat userdev interface test");
+}
+
+ATF_TC_BODY(sndstat_udev, tc)
+{
+	nvlist_t *nvl, *di, *dichild;
+	struct sndstioc_nv_arg arg;
+	int fd, rc;
+
+	load_dummy();
+
+	if ((fd = open("/dev/sndstat", O_RDWR)) < 0)
+		atf_tc_skip("/dev/sndstat not found, load sound(4)");
+
+	nvl = nvlist_create(0);
+	ATF_REQUIRE(nvl != NULL);
+
+	di = nvlist_create(0);
+	ATF_REQUIRE(di != NULL);
+
+	dichild = nvlist_create(0);
+	ATF_REQUIRE(dichild != NULL);
+
+	nvlist_add_string(di, SNDST_DSPS_PROVIDER, "sndstat_udev");
+	nvlist_add_string(di, SNDST_DSPS_NAMEUNIT, "sndstat_udev");
+	nvlist_add_string(di, SNDST_DSPS_DESC, "Test Device");
+	nvlist_add_string(di, SNDST_DSPS_DEVNODE, "sndstat_udev");
+	nvlist_add_number(di, SNDST_DSPS_PCHAN, 1);
+	nvlist_add_number(di, SNDST_DSPS_RCHAN, 2);
+
+	nvlist_add_number(dichild, SNDST_DSPS_INFO_MIN_RATE, 8000);
+	nvlist_add_number(dichild, SNDST_DSPS_INFO_MAX_RATE, 96000);
+	nvlist_add_number(dichild, SNDST_DSPS_INFO_FORMATS,
+	    AFMT_S16_NE | AFMT_S24_NE | AFMT_S32_NE);
+	nvlist_add_number(dichild, SNDST_DSPS_INFO_MIN_CHN, 1);
+	nvlist_add_number(dichild, SNDST_DSPS_INFO_MAX_CHN, 2);
+
+	nvlist_add_nvlist(di, SNDST_DSPS_INFO_PLAY, dichild);
+	nvlist_add_nvlist(di, SNDST_DSPS_INFO_REC, dichild);
+
+	nvlist_append_nvlist_array(nvl, SNDST_DSPS, di);
+	ATF_REQUIRE_EQ(nvlist_error(nvl), 0);
+
+	arg.buf = nvlist_pack(nvl, &arg.nbytes);
+	ATF_REQUIRE_MSG(arg.buf != NULL, "failed to pack nvlist");
+
+	rc = ioctl(fd, SNDSTIOC_ADD_USER_DEVS, &arg);
+	free(arg.buf);
+	ATF_REQUIRE_EQ_MSG(rc, 0, "ioctl(SNDSTIOC_ADD_USER_DEVS) failed");
+
+	nvlist_destroy(di);
+	nvlist_destroy(dichild);
+	nvlist_destroy(nvl);
+
+	/* Read back registered values. */
+	read_all(fd);
 	close(fd);
 }
 
 ATF_TP_ADD_TCS(tp)
 {
 	ATF_TP_ADD_TC(tp, sndstat_nv);
+	ATF_TP_ADD_TC(tp, sndstat_udev);
 
 	return (atf_no_error());
 }