diff --git a/tests/Makefile.am b/tests/Makefile.am
index 91f042e..54fb11f 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -27,6 +27,9 @@
 		 oap/oap_client_test gsm29205/gsm29205_test		\
 		 logging/logging_vty_test				\
 		 vty/vty_transcript_test				\
+		 tdef/tdef_test tdef/tdef_vty_test_config_root		\
+		 tdef/tdef_vty_test_config_subnode			\
+		 tdef/tdef_vty_test_dynamic				\
 		 $(NULL)
 
 if ENABLE_MSGFILE
@@ -221,6 +224,18 @@
 gsm23003_gsm23003_test_SOURCES = gsm23003/gsm23003_test.c
 gsm23003_gsm23003_test_LDADD = $(LDADD) $(top_builddir)/src/gsm/libosmogsm.la
 
+tdef_tdef_test_SOURCES = tdef/tdef_test.c
+tdef_tdef_test_LDADD = $(LDADD)
+
+tdef_tdef_vty_test_config_root_SOURCES = tdef/tdef_vty_test_config_root.c
+tdef_tdef_vty_test_config_root_LDADD = $(LDADD) $(top_builddir)/src/vty/libosmovty.la
+
+tdef_tdef_vty_test_config_subnode_SOURCES = tdef/tdef_vty_test_config_subnode.c
+tdef_tdef_vty_test_config_subnode_LDADD = $(LDADD) $(top_builddir)/src/vty/libosmovty.la
+
+tdef_tdef_vty_test_dynamic_SOURCES = tdef/tdef_vty_test_dynamic.c
+tdef_tdef_vty_test_dynamic_LDADD = $(LDADD) $(top_builddir)/src/vty/libosmovty.la
+
 # The `:;' works around a Bash 3.2 bug when the output is not writeable.
 $(srcdir)/package.m4: $(top_srcdir)/configure.ac
 	:;{ \
@@ -284,6 +299,10 @@
 	     timer/clk_override_test.ok					\
 	     oap/oap_client_test.ok oap/oap_client_test.err		\
 	     vty/vty_transcript_test.vty				\
+	     tdef/tdef_test.ok \
+	     tdef/tdef_vty_test_config_root.vty	\
+	     tdef/tdef_vty_test_config_subnode.vty \
+	     tdef/tdef_vty_test_dynamic.vty \
 	     $(NULL)
 
 DISTCLEANFILES = atconfig atlocal conv/gsm0503_test_vectors.c
@@ -328,6 +347,7 @@
 # To update the VTY script from current application behavior,
 # pass -u to osmo_verify_transcript_vty.py by doing:
 #   make vty-test U=-u
+
 vty-test-logging:
 	osmo_verify_transcript_vty.py -v \
 		-p 42042 \
@@ -340,9 +360,25 @@
 		-r "$(top_builddir)/tests/vty/vty_transcript_test" \
 		$(U) $(srcdir)/vty/*.vty
 
+vty-test-tdef:
+	osmo_verify_transcript_vty.py -v \
+		-p 42042 \
+		-r "$(top_builddir)/tests/tdef/tdef_vty_test_config_root" \
+		$(U) $(srcdir)/tdef/tdef_vty_test_config_root.vty
+	osmo_verify_transcript_vty.py -v \
+		-p 42042 \
+		-r "$(top_builddir)/tests/tdef/tdef_vty_test_config_subnode" \
+		$(U) $(srcdir)/tdef/tdef_vty_test_config_subnode.vty
+	osmo_verify_transcript_vty.py -v \
+		-p 42042 \
+		-r "$(top_builddir)/tests/tdef/tdef_vty_test_dynamic" \
+		$(U) $(srcdir)/tdef/tdef_vty_test_dynamic.vty
+
+# don't run vty tests concurrently so that the ports don't conflict
 vty-test:
 	$(MAKE) vty-test-logging
 	$(MAKE) vty-test-vty
+	$(MAKE) vty-test-tdef
 
 ctrl-test:
 	echo "No CTRL tests exist currently"
diff --git a/tests/tdef/tdef_test.c b/tests/tdef/tdef_test.c
new file mode 100644
index 0000000..682c7ac
--- /dev/null
+++ b/tests/tdef/tdef_test.c
@@ -0,0 +1,445 @@
+/* Test implementation for osmo_tdef API. */
+/*
+ * (C) 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * Author: Neels Hofmeyr <neels@hofmeyr.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <stdio.h>
+#include <errno.h>
+#include <limits.h>
+
+#include <osmocom/core/logging.h>
+#include <osmocom/core/application.h>
+#include <osmocom/core/fsm.h>
+
+#include <osmocom/core/tdef.h>
+
+static void *ctx = NULL;
+
+static struct osmo_tdef tdefs[] = {
+	{ .T=1, .default_val=100, .desc="100s" },
+	{ .T=2, .default_val=100, .unit=OSMO_TDEF_MS, .desc="100ms" },
+	{ .T=3, .default_val=100, .unit=OSMO_TDEF_M, .desc="100m" },
+	{ .T=4, .default_val=100, .unit=OSMO_TDEF_CUSTOM, .desc="100 potatoes" },
+
+	{ .T=7, .default_val=50, .desc="Water Boiling Timeout" },  // default is .unit=OSMO_TDEF_S == 0
+	{ .T=8, .default_val=300, .desc="Tea brewing" },
+	{ .T=9, .default_val=5, .unit=OSMO_TDEF_M, .desc="Let tea cool down before drinking" },
+	{ .T=10, .default_val=20, .unit=OSMO_TDEF_M, .desc="Forgot to drink tea while it's warm" },
+
+	/* test conversions */
+	{ .T=1000, .default_val=2*1000, .unit=OSMO_TDEF_MS, .desc="two seconds from ms" },
+	{ .T=1001, .default_val=60*1000, .unit=OSMO_TDEF_MS, .desc="one minute from ms" },
+	{ .T=1002, .default_val=(ULONG_MAX/60), .unit=OSMO_TDEF_M, .desc="almost too many seconds" },
+	{ .T=1003, .default_val=ULONG_MAX, .unit=OSMO_TDEF_M, .desc="too many seconds" },
+	{ .T=1004, .default_val=1, .unit=OSMO_TDEF_MS, .desc="one ms" },
+	{ .T=1005, .default_val=0, .unit=OSMO_TDEF_MS, .desc="zero ms" },
+	{ .T=1006, .default_val=0, .unit=OSMO_TDEF_S, .desc="zero s" },
+	{ .T=1007, .default_val=0, .unit=OSMO_TDEF_M, .desc="zero m" },
+	{ .T=1008, .default_val=0, .unit=OSMO_TDEF_CUSTOM, .desc="zero" },
+
+	/* test range */
+	{ .T=INT_MAX, .default_val=ULONG_MAX, .unit=OSMO_TDEF_S, .desc="very large" },
+	{ .T=INT_MAX-1, .default_val=ULONG_MAX-1, .unit=OSMO_TDEF_S, .desc="very large" },
+	{ .T=INT_MAX-2, .default_val=LONG_MAX, .unit=OSMO_TDEF_S, .desc="very large" },
+	{ .T=INT_MAX-3, .default_val=ULONG_MAX, .unit=OSMO_TDEF_M, .desc="very large in minutes" },
+	{ .T=INT_MIN, .default_val=ULONG_MAX, .unit=OSMO_TDEF_S, .desc="negative" },
+
+	{ .T=0, .default_val=1, .unit=OSMO_TDEF_CUSTOM, .desc="zero" },
+
+	/* no desc */
+	{ .T=123, .default_val=1 },
+
+	{}  //  <-- important! last entry shall be zero
+};
+
+#define print_tdef_get(T, AS_UNIT) do { \
+		unsigned long val = osmo_tdef_get(tdefs, T, AS_UNIT, 999); \
+		printf("osmo_tdef_get(tdefs, %d, %s, 999)\t= %lu\n", T, osmo_tdef_unit_name(AS_UNIT), val); \
+	} while (0)
+
+#define print_tdef_get_short(T, AS_UNIT) do { \
+		unsigned long val = osmo_tdef_get(tdefs, T, AS_UNIT, 999); \
+		printf("osmo_tdef_get(%d, %s)\t= %lu\n", T, osmo_tdef_unit_name(AS_UNIT), val); \
+	} while (0)
+
+void print_tdef_info(unsigned int T)
+{
+	const struct osmo_tdef *t = osmo_tdef_get_entry(tdefs, T);
+	if (!t) {
+		printf("T%d=NULL", T);
+		return;
+	}
+	printf("T%d=%lu%s", T, t->val, osmo_tdef_unit_name(t->unit));
+	if (t->val != t->default_val)
+		printf("(def=%lu)", t->default_val);
+	printf("\n");
+}
+
+static void test_tdef_get()
+{
+	int i;
+	enum osmo_tdef_unit as_unit;
+
+	printf("\n%s()\n", __func__);
+
+	osmo_tdefs_reset(tdefs); // make all values the default
+
+	for (i = 0; i < ARRAY_SIZE(tdefs)-1; i++) {
+		unsigned int T = tdefs[i].T;
+		print_tdef_info(T);
+		for (as_unit = OSMO_TDEF_S; as_unit <= OSMO_TDEF_CUSTOM; as_unit++) {
+			print_tdef_get_short(T, as_unit);
+		}
+	}
+}
+
+static void test_tdef_get_nonexisting()
+{
+	printf("\n%s()\n", __func__);
+
+	print_tdef_get(5, OSMO_TDEF_S);
+	print_tdef_get(5, OSMO_TDEF_MS);
+	print_tdef_get(5, OSMO_TDEF_M);
+	print_tdef_get(5, OSMO_TDEF_CUSTOM);
+}
+
+static void test_tdef_set_and_get()
+{
+	struct osmo_tdef *t;
+	printf("\n%s()\n", __func__);
+
+	t = osmo_tdef_get_entry(tdefs, 7);
+	printf("setting 7 = 42\n");
+	t->val = 42;
+	print_tdef_info(7);
+	print_tdef_get_short(7, OSMO_TDEF_MS);
+	print_tdef_get_short(7, OSMO_TDEF_S);
+	print_tdef_get_short(7, OSMO_TDEF_M);
+	print_tdef_get_short(7, OSMO_TDEF_CUSTOM);
+
+	printf("setting 7 = 420\n");
+	t->val = 420;
+	print_tdef_info(7);
+	print_tdef_get_short(7, OSMO_TDEF_MS);
+	print_tdef_get_short(7, OSMO_TDEF_S);
+	print_tdef_get_short(7, OSMO_TDEF_M);
+	print_tdef_get_short(7, OSMO_TDEF_CUSTOM);
+
+	printf("resetting\n");
+	osmo_tdefs_reset(tdefs);
+	print_tdef_info(7);
+	print_tdef_get_short(7, OSMO_TDEF_S);
+}
+
+enum test_tdef_fsm_states {
+	S_A = 0,
+	S_B,
+	S_C,
+	S_D,
+	S_G,
+	S_H,
+	S_I,
+	S_J,
+	S_K,
+	S_L,
+	S_M,
+	S_N,
+	S_O,
+	S_X,
+	S_Y,
+	S_Z,
+};
+
+static const struct osmo_tdef_state_timeout test_tdef_state_timeouts[32] = {
+	[S_A] = { .T = 1 },
+	[S_B] = { .T = 2 },
+	[S_C] = { .T = 3 },
+	[S_D] = { .T = 4 },
+
+	[S_G] = { .T = 7 },
+	[S_H] = { .T = 8 },
+	[S_I] = { .T = 9 },
+	[S_J] = { .T = 10 },
+
+	/* keep_timer: adopt whichever T was running before and continue the timeout. */
+	[S_K] = { .keep_timer = true },
+	/* S_F defines an undefined T, but should continue previous state's timeout. */
+	[S_L] = { .T = 123, .keep_timer = true },
+
+	/* range */
+	[S_M] = { .T = INT_MAX },
+	[S_N] = { .T = INT_MIN },
+
+	/* T0 is not addressable from osmo_tdef_state_timeout, since it is indistinguishable from an unset entry. Even
+	 * though a timeout value is set for T=0, the transition to state S_O will show "no timer configured". */
+	[S_O] = { .T = 0 },
+
+	/* S_X undefined on purpose */
+	/* S_Y defines a T that does not exist */
+	[S_Y] = { .T = 666 },
+	/* S_Z undefined on purpose */
+};
+
+#define S(x)	(1 << (x))
+
+static const struct osmo_fsm_state test_tdef_fsm_states[] = {
+#define DEF_STATE(NAME) \
+	[S_##NAME] = { \
+		.name = #NAME, \
+		.out_state_mask = 0 \
+			| S(S_A) \
+			| S(S_B) \
+			| S(S_C) \
+			| S(S_D) \
+			| S(S_G) \
+			| S(S_H) \
+			| S(S_I) \
+			| S(S_J) \
+			| S(S_K) \
+			| S(S_L) \
+			| S(S_M) \
+			| S(S_N) \
+			| S(S_O) \
+			| S(S_X) \
+			| S(S_Y) \
+			| S(S_Z) \
+			, \
+	}
+
+	DEF_STATE(A),
+	DEF_STATE(B),
+	DEF_STATE(C),
+	DEF_STATE(D),
+
+	DEF_STATE(G),
+	DEF_STATE(H),
+	DEF_STATE(I),
+	DEF_STATE(J),
+
+	DEF_STATE(K),
+	DEF_STATE(L),
+
+	DEF_STATE(M),
+	DEF_STATE(N),
+	DEF_STATE(O),
+
+	DEF_STATE(X),
+	DEF_STATE(Y),
+	/* Z: test not being allowed to transition to other states. */
+	[S_Z] = {
+		.name = "Z",
+		.out_state_mask = 0
+			| S(S_A)
+			,
+	},
+};
+
+static const struct value_string test_tdef_fsm_event_names[] = { {} };
+
+static struct osmo_fsm test_tdef_fsm = {
+	.name = "tdef_test",
+	.states = test_tdef_fsm_states,
+	.event_names = test_tdef_fsm_event_names,
+	.num_states = ARRAY_SIZE(test_tdef_fsm_states),
+	.log_subsys = DLGLOBAL,
+};
+
+const struct timeval fake_time_start_time = { 123, 456 };
+
+#define fake_time_passes(secs, usecs) do \
+{ \
+	struct timeval diff; \
+	osmo_gettimeofday_override_add(secs, usecs); \
+	osmo_clock_override_add(CLOCK_MONOTONIC, secs, usecs * 1000); \
+	timersub(&osmo_gettimeofday_override_time, &fake_time_start_time, &diff); \
+	printf("Total time passed: %ld.%06ld s\n", diff.tv_sec, diff.tv_usec); \
+	osmo_timers_prepare(); \
+	osmo_timers_update(); \
+} while (0)
+
+void fake_time_start()
+{
+	struct timespec *clock_override;
+
+	osmo_gettimeofday_override_time = fake_time_start_time;
+	osmo_gettimeofday_override = true;
+	clock_override = osmo_clock_override_gettimespec(CLOCK_MONOTONIC);
+	OSMO_ASSERT(clock_override);
+	clock_override->tv_sec = fake_time_start_time.tv_sec;
+	clock_override->tv_nsec = fake_time_start_time.tv_usec * 1000;
+	osmo_clock_override_enable(CLOCK_MONOTONIC, true);
+	fake_time_passes(0, 0);
+}
+
+static void print_fsm_state(struct osmo_fsm_inst *fi)
+{
+	struct timeval remaining;
+	printf("state=%s T=%d", osmo_fsm_inst_state_name(fi), fi->T);
+
+	if (!osmo_timer_pending(&fi->timer)) {
+		printf(", no timeout\n");
+		return;
+	}
+
+	osmo_timer_remaining(&fi->timer, &osmo_gettimeofday_override_time, &remaining);
+	printf(", %lu.%06lu s remaining\n", remaining.tv_sec, remaining.tv_usec);
+}
+
+
+#define test_tdef_fsm_state_chg(NEXT_STATE) do { \
+		const struct osmo_tdef_state_timeout *st = osmo_tdef_get_state_timeout(NEXT_STATE, \
+										       test_tdef_state_timeouts); \
+		if (!st) { \
+			printf(" --> %s (no timer configured for this state)\n", \
+			       osmo_fsm_state_name(&test_tdef_fsm, NEXT_STATE)); \
+		} else { \
+			struct osmo_tdef *t = osmo_tdef_get_entry(tdefs, st->T); \
+			int rc = osmo_tdef_fsm_inst_state_chg(fi, NEXT_STATE, test_tdef_state_timeouts, tdefs, 999); \
+			printf(" --> %s (configured as T%d%s %lu %s) rc=%d;\t", osmo_fsm_state_name(&test_tdef_fsm, \
+												    NEXT_STATE), \
+			       st->T, st->keep_timer ? "(keep_timer)" : "", \
+			       t? t->val : -1, t? osmo_tdef_unit_name(t->unit) : "-", \
+			       rc); \
+			print_fsm_state(fi); \
+		} \
+	} while(0)
+
+
+
+static void test_tdef_state_timeout(bool test_range)
+{
+	struct osmo_fsm_inst *fi;
+	struct osmo_tdef *m = osmo_tdef_get_entry(tdefs, INT_MAX);
+	unsigned long m_secs;
+	printf("\n%s()\n", __func__);
+
+	osmo_tdefs_reset(tdefs);
+
+	fake_time_start();
+
+	fi = osmo_fsm_inst_alloc(&test_tdef_fsm, ctx, NULL, LOGL_DEBUG, __func__);
+	OSMO_ASSERT(fi);
+	print_fsm_state(fi);
+
+	test_tdef_fsm_state_chg(S_A);
+	test_tdef_fsm_state_chg(S_B);
+	test_tdef_fsm_state_chg(S_C);
+	test_tdef_fsm_state_chg(S_D);
+
+	test_tdef_fsm_state_chg(S_G);
+	test_tdef_fsm_state_chg(S_H);
+	test_tdef_fsm_state_chg(S_I);
+	test_tdef_fsm_state_chg(S_J);
+
+	printf("- test keep_timer:\n");
+	fake_time_passes(123, 45678);
+	print_fsm_state(fi);
+	test_tdef_fsm_state_chg(S_K);
+	test_tdef_fsm_state_chg(S_A);
+	fake_time_passes(23, 45678);
+	print_fsm_state(fi);
+	test_tdef_fsm_state_chg(S_K);
+
+	test_tdef_fsm_state_chg(S_A);
+	fake_time_passes(23, 45678);
+	print_fsm_state(fi);
+	test_tdef_fsm_state_chg(S_L);
+
+	printf("- test large T:\n");
+	test_tdef_fsm_state_chg(S_M);
+
+	printf("- test T<0:\n");
+	test_tdef_fsm_state_chg(S_N);
+
+	printf("- test T=0:\n");
+	test_tdef_fsm_state_chg(S_O);
+
+	printf("- test no timer:\n");
+	test_tdef_fsm_state_chg(S_X);
+
+	printf("- test undefined timer, using default_val arg of osmo_tdef_fsm_inst_state_chg(), here passed as 999:\n");
+	test_tdef_fsm_state_chg(S_Y);
+
+	/* the range of unsigned long is architecture dependent. This test can be invoked manually to see whether
+	 * clamping the timeout values works, but the output will be of varying lengths depending on the system's
+	 * unsigned long range, and would cause differences in expected output. */
+	if (test_range) {
+		printf("- test range:\n");
+		test_tdef_fsm_state_chg(S_M);
+		/* sweep through all the bits, shifting in 0xfffff.. from the right. */
+		m_secs = 0;
+		do {
+			m_secs = (m_secs << 1) + 1;
+			switch (m_secs) {
+			case 0x7fff:
+				printf("--- int32_t max ---\n");
+				break;
+			case 0xffff:
+				printf("--- uint32_t max ---\n");
+				break;
+			case 0x7fffffff:
+				printf("--- int64_t max ---\n");
+				break;
+			case 0xffffffff:
+				printf("--- uint64_t max ---\n");
+				break;
+			default:
+				break;
+			}
+
+			m->val = m_secs - 1;
+			test_tdef_fsm_state_chg(S_M);
+			m->val = m_secs;
+			test_tdef_fsm_state_chg(S_M);
+			m->val = m_secs + 1;
+			test_tdef_fsm_state_chg(S_M);
+		} while (m_secs < ULONG_MAX);
+	}
+
+	printf("- test disallowed transition:\n");
+	test_tdef_fsm_state_chg(S_Z);
+	test_tdef_fsm_state_chg(S_B);
+	test_tdef_fsm_state_chg(S_C);
+	test_tdef_fsm_state_chg(S_D);
+}
+
+int main(int argc, char **argv)
+{
+	ctx = talloc_named_const(NULL, 0, "tdef_test.c");
+	osmo_init_logging2(ctx, NULL);
+
+	log_set_print_filename(osmo_stderr_target, 0);
+	log_set_print_category(osmo_stderr_target, 1);
+	log_set_use_color(osmo_stderr_target, 0);
+
+	osmo_fsm_register(&test_tdef_fsm);
+
+	test_tdef_get();
+	test_tdef_get_nonexisting();
+	test_tdef_set_and_get();
+	/* Run range test iff any argument is passed on the cmdline. For the rationale, see the comment in
+	 * test_tdef_state_timeout(). */
+	test_tdef_state_timeout(argc > 1);
+
+	return EXIT_SUCCESS;
+}
diff --git a/tests/tdef/tdef_test.ok b/tests/tdef/tdef_test.ok
new file mode 100644
index 0000000..cf4b77f
--- /dev/null
+++ b/tests/tdef/tdef_test.ok
@@ -0,0 +1,184 @@
+
+test_tdef_get()
+T1=100s
+osmo_tdef_get(1, s)	= 100
+osmo_tdef_get(1, ms)	= 100000
+osmo_tdef_get(1, m)	= 2
+osmo_tdef_get(1, custom-unit)	= 100
+T2=100ms
+osmo_tdef_get(2, s)	= 1
+osmo_tdef_get(2, ms)	= 100
+osmo_tdef_get(2, m)	= 1
+osmo_tdef_get(2, custom-unit)	= 100
+T3=100m
+osmo_tdef_get(3, s)	= 6000
+osmo_tdef_get(3, ms)	= 6000000
+osmo_tdef_get(3, m)	= 100
+osmo_tdef_get(3, custom-unit)	= 100
+T4=100custom-unit
+osmo_tdef_get(4, s)	= 100
+osmo_tdef_get(4, ms)	= 100
+osmo_tdef_get(4, m)	= 100
+osmo_tdef_get(4, custom-unit)	= 100
+T7=50s
+osmo_tdef_get(7, s)	= 50
+osmo_tdef_get(7, ms)	= 50000
+osmo_tdef_get(7, m)	= 1
+osmo_tdef_get(7, custom-unit)	= 50
+T8=300s
+osmo_tdef_get(8, s)	= 300
+osmo_tdef_get(8, ms)	= 300000
+osmo_tdef_get(8, m)	= 5
+osmo_tdef_get(8, custom-unit)	= 300
+T9=5m
+osmo_tdef_get(9, s)	= 300
+osmo_tdef_get(9, ms)	= 300000
+osmo_tdef_get(9, m)	= 5
+osmo_tdef_get(9, custom-unit)	= 5
+T10=20m
+osmo_tdef_get(10, s)	= 1200
+osmo_tdef_get(10, ms)	= 1200000
+osmo_tdef_get(10, m)	= 20
+osmo_tdef_get(10, custom-unit)	= 20
+T1000=2000ms
+osmo_tdef_get(1000, s)	= 2
+osmo_tdef_get(1000, ms)	= 2000
+osmo_tdef_get(1000, m)	= 1
+osmo_tdef_get(1000, custom-unit)	= 2000
+T1001=60000ms
+osmo_tdef_get(1001, s)	= 60
+osmo_tdef_get(1001, ms)	= 60000
+osmo_tdef_get(1001, m)	= 1
+osmo_tdef_get(1001, custom-unit)	= 60000
+T1002=307445734561825860m
+osmo_tdef_get(1002, s)	= 18446744073709551600
+osmo_tdef_get(1002, ms)	= 18446744073709551615
+osmo_tdef_get(1002, m)	= 307445734561825860
+osmo_tdef_get(1002, custom-unit)	= 307445734561825860
+T1003=18446744073709551615m
+osmo_tdef_get(1003, s)	= 18446744073709551615
+osmo_tdef_get(1003, ms)	= 18446744073709551615
+osmo_tdef_get(1003, m)	= 18446744073709551615
+osmo_tdef_get(1003, custom-unit)	= 18446744073709551615
+T1004=1ms
+osmo_tdef_get(1004, s)	= 1
+osmo_tdef_get(1004, ms)	= 1
+osmo_tdef_get(1004, m)	= 1
+osmo_tdef_get(1004, custom-unit)	= 1
+T1005=0ms
+osmo_tdef_get(1005, s)	= 0
+osmo_tdef_get(1005, ms)	= 0
+osmo_tdef_get(1005, m)	= 0
+osmo_tdef_get(1005, custom-unit)	= 0
+T1006=0s
+osmo_tdef_get(1006, s)	= 0
+osmo_tdef_get(1006, ms)	= 0
+osmo_tdef_get(1006, m)	= 0
+osmo_tdef_get(1006, custom-unit)	= 0
+T1007=0m
+osmo_tdef_get(1007, s)	= 0
+osmo_tdef_get(1007, ms)	= 0
+osmo_tdef_get(1007, m)	= 0
+osmo_tdef_get(1007, custom-unit)	= 0
+T1008=0custom-unit
+osmo_tdef_get(1008, s)	= 0
+osmo_tdef_get(1008, ms)	= 0
+osmo_tdef_get(1008, m)	= 0
+osmo_tdef_get(1008, custom-unit)	= 0
+T2147483647=18446744073709551615s
+osmo_tdef_get(2147483647, s)	= 18446744073709551615
+osmo_tdef_get(2147483647, ms)	= 18446744073709551615
+osmo_tdef_get(2147483647, m)	= 307445734561825861
+osmo_tdef_get(2147483647, custom-unit)	= 18446744073709551615
+T2147483646=18446744073709551614s
+osmo_tdef_get(2147483646, s)	= 18446744073709551614
+osmo_tdef_get(2147483646, ms)	= 18446744073709551615
+osmo_tdef_get(2147483646, m)	= 307445734561825861
+osmo_tdef_get(2147483646, custom-unit)	= 18446744073709551614
+T2147483645=9223372036854775807s
+osmo_tdef_get(2147483645, s)	= 9223372036854775807
+osmo_tdef_get(2147483645, ms)	= 18446744073709551615
+osmo_tdef_get(2147483645, m)	= 153722867280912931
+osmo_tdef_get(2147483645, custom-unit)	= 9223372036854775807
+T2147483644=18446744073709551615m
+osmo_tdef_get(2147483644, s)	= 18446744073709551615
+osmo_tdef_get(2147483644, ms)	= 18446744073709551615
+osmo_tdef_get(2147483644, m)	= 18446744073709551615
+osmo_tdef_get(2147483644, custom-unit)	= 18446744073709551615
+T-2147483648=18446744073709551615s
+osmo_tdef_get(-2147483648, s)	= 18446744073709551615
+osmo_tdef_get(-2147483648, ms)	= 18446744073709551615
+osmo_tdef_get(-2147483648, m)	= 307445734561825861
+osmo_tdef_get(-2147483648, custom-unit)	= 18446744073709551615
+T0=1custom-unit
+osmo_tdef_get(0, s)	= 1
+osmo_tdef_get(0, ms)	= 1
+osmo_tdef_get(0, m)	= 1
+osmo_tdef_get(0, custom-unit)	= 1
+T123=1s
+osmo_tdef_get(123, s)	= 1
+osmo_tdef_get(123, ms)	= 1000
+osmo_tdef_get(123, m)	= 1
+osmo_tdef_get(123, custom-unit)	= 1
+
+test_tdef_get_nonexisting()
+osmo_tdef_get(tdefs, 5, s, 999)	= 999
+osmo_tdef_get(tdefs, 5, ms, 999)	= 999
+osmo_tdef_get(tdefs, 5, m, 999)	= 999
+osmo_tdef_get(tdefs, 5, custom-unit, 999)	= 999
+
+test_tdef_set_and_get()
+setting 7 = 42
+T7=42s(def=50)
+osmo_tdef_get(7, ms)	= 42000
+osmo_tdef_get(7, s)	= 42
+osmo_tdef_get(7, m)	= 1
+osmo_tdef_get(7, custom-unit)	= 42
+setting 7 = 420
+T7=420s(def=50)
+osmo_tdef_get(7, ms)	= 420000
+osmo_tdef_get(7, s)	= 420
+osmo_tdef_get(7, m)	= 7
+osmo_tdef_get(7, custom-unit)	= 420
+resetting
+T7=50s
+osmo_tdef_get(7, s)	= 50
+
+test_tdef_state_timeout()
+Total time passed: 0.000000 s
+state=A T=0, no timeout
+ --> A (configured as T1 100 s) rc=0;	state=A T=1, 100.000000 s remaining
+ --> B (configured as T2 100 ms) rc=0;	state=B T=2, 1.000000 s remaining
+ --> C (configured as T3 100 m) rc=0;	state=C T=3, 6000.000000 s remaining
+ --> D (configured as T4 100 custom-unit) rc=0;	state=D T=4, 100.000000 s remaining
+ --> G (configured as T7 50 s) rc=0;	state=G T=7, 50.000000 s remaining
+ --> H (configured as T8 300 s) rc=0;	state=H T=8, 300.000000 s remaining
+ --> I (configured as T9 5 m) rc=0;	state=I T=9, 300.000000 s remaining
+ --> J (configured as T10 20 m) rc=0;	state=J T=10, 1200.000000 s remaining
+- test keep_timer:
+Total time passed: 123.045678 s
+state=J T=10, 1076.954322 s remaining
+ --> K (configured as T0(keep_timer) 1 custom-unit) rc=0;	state=K T=10, 1076.954322 s remaining
+ --> A (configured as T1 100 s) rc=0;	state=A T=1, 100.000000 s remaining
+Total time passed: 146.091356 s
+state=A T=1, 76.954322 s remaining
+ --> K (configured as T0(keep_timer) 1 custom-unit) rc=0;	state=K T=1, 76.954322 s remaining
+ --> A (configured as T1 100 s) rc=0;	state=A T=1, 100.000000 s remaining
+Total time passed: 169.137034 s
+state=A T=1, 76.954322 s remaining
+ --> L (configured as T123(keep_timer) 1 s) rc=0;	state=L T=123, 76.954322 s remaining
+- test large T:
+ --> M (configured as T2147483647 18446744073709551615 s) rc=0;	state=M T=2147483647, 2147483647.000000 s remaining
+- test T<0:
+ --> N (configured as T-2147483648 18446744073709551615 s) rc=0;	state=N T=-2147483648, 2147483647.000000 s remaining
+- test T=0:
+ --> O (no timer configured for this state)
+- test no timer:
+ --> X (no timer configured for this state)
+- test undefined timer, using default_val arg of osmo_tdef_fsm_inst_state_chg(), here passed as 999:
+ --> Y (configured as T666 18446744073709551615 -) rc=0;	state=Y T=666, 999.000000 s remaining
+- test disallowed transition:
+ --> Z (no timer configured for this state)
+ --> B (configured as T2 100 ms) rc=0;	state=B T=2, 1.000000 s remaining
+ --> C (configured as T3 100 m) rc=0;	state=C T=3, 6000.000000 s remaining
+ --> D (configured as T4 100 custom-unit) rc=0;	state=D T=4, 100.000000 s remaining
diff --git a/tests/tdef/tdef_vty_test_config_root.c b/tests/tdef/tdef_vty_test_config_root.c
new file mode 100644
index 0000000..138ac00
--- /dev/null
+++ b/tests/tdef/tdef_vty_test_config_root.c
@@ -0,0 +1,292 @@
+/* Test implementation for osmo_tdef VTY configuration API. */
+/*
+ * (C) 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * Author: Neels Hofmeyr <nhofmeyr@sysmocom.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#define _GNU_SOURCE
+#include <getopt.h>
+#include <signal.h>
+#include <limits.h>
+#include <string.h>
+
+#include <osmocom/core/application.h>
+
+#include <osmocom/vty/command.h>
+#include <osmocom/vty/misc.h>
+#include <osmocom/vty/telnet_interface.h>
+
+#include <osmocom/core/tdef.h>
+#include <osmocom/vty/tdef_vty.h>
+
+#include <stdlib.h>
+
+#include "config.h"
+
+/* ------------------- HERE IS THE INTERESTING TDEF RELEVANT PART ------------------- */
+
+/* This example keeps several separate timer groups and offers 'timer' VTY commands at the root of the config node. See
+ * the tdef_vty_test_config_root.vty transcript test.
+ */
+
+static struct osmo_tdef tdefs_test[] = {
+	{ .T=1, .default_val=100, .desc="Testing a hundred seconds" },  // default is .unit=OSMO_TDEF_S == 0
+	{ .T=2, .default_val=100, .unit=OSMO_TDEF_MS, .desc="Testing a hundred milliseconds" },
+	{ .T=3, .default_val=100, .unit=OSMO_TDEF_M, .desc="Testing a hundred minutes" },
+	{ .T=4, .default_val=100, .unit=OSMO_TDEF_CUSTOM, .desc="Testing a hundred potatoes" },
+	{ .T=INT_MAX, .default_val=ULONG_MAX, .unit=OSMO_TDEF_M, .desc="Very large" },
+	{ .T=-23, .default_val=-15, .desc="Negative T number" },
+	{}  //  <-- important! last entry shall be zero
+};
+
+static struct osmo_tdef tdefs_tea[] = {
+	{ .T=1, .default_val=50, .desc="Water Boiling Timeout" },
+	{ .T=2, .default_val=300, .desc="Tea brewing" },
+	{ .T=3, .default_val=5, .unit=OSMO_TDEF_M, .desc="Let tea cool down before drinking" },
+	{ .T=4, .default_val=20, .unit=OSMO_TDEF_M, .desc="Forgot to drink tea while it's warm" },
+	{}
+};
+
+static struct osmo_tdef tdefs_software[] = {
+	{ .T=1, .default_val=30, .unit=OSMO_TDEF_M, .desc="Write code" },
+	{ .T=2, .default_val=20, .unit=OSMO_TDEF_MS, .desc="Hit segfault" },
+	{ .T=3, .default_val=480, .unit=OSMO_TDEF_M, .desc="Fix bugs" },
+	{}
+};
+
+static struct osmo_tdef_group tdef_groups[] = {
+	{
+		.name = "tea",
+		.desc = "Tea time",
+		.tdefs = tdefs_tea,
+	},
+	{
+		.name = "test",
+		.desc = "Test timers",
+		.tdefs = tdefs_test,
+	},
+	{
+		.name = "software",
+		.desc = "Typical software development cycle",
+		.tdefs = tdefs_software,
+	},
+	{}
+};
+
+enum tdef_vty_test_nodes {
+	TIMER_NODE = _LAST_OSMOVTY_NODE + 1,
+};
+
+/* This example puts 'timer' configuration commands directly at the root of the CONFIG_NODE.
+ * This TIMER_NODE is merely needed as a hook for the vty_write() command, but becomes an empty node in the VTY docs.
+ * It is possible to cheat around needing this if you choose to config_write_timer() in another root nodes' write cb.
+ * Another example using a 'network' subnode is \ref tdef_vty_test_config_subnode.c */
+static struct cmd_node timer_node = {
+	TIMER_NODE,
+	"%s(config-timer)# ",
+	1,
+};
+
+static int config_write_timer(struct vty *vty)
+{
+	osmo_tdef_vty_groups_write(vty, "");
+	return CMD_SUCCESS;
+}
+
+static void timer_init_vty()
+{
+	/* Again, this is merely to get a vty write hook, see above. */
+	install_node(&timer_node, config_write_timer);
+
+	osmo_tdef_vty_groups_init(CONFIG_NODE, tdef_groups);
+}
+
+/* ------------------- THE REST is just boilerplate osmo main() ------------------- */
+
+void *root_ctx = NULL;
+
+static void print_help()
+{
+	printf( "options:\n"
+		"  -h	--help		this text\n"
+		"  -d	--debug MASK	Enable debugging (e.g. -d DRSL:DOML:DLAPDM)\n"
+		"  -D	--daemonize	For the process into a background daemon\n"
+		"  -c	--config-file	Specify the filename of the config file\n"
+		"  -s	--disable-color	Don't use colors in stderr log output\n"
+		"  -T	--timestamp	Prefix every log line with a timestamp\n"
+		"  -V	--version	Print version information and exit\n"
+		"  -e	--log-level	Set a global log-level\n"
+		);
+}
+
+static struct {
+	const char *config_file;
+	int daemonize;
+} cmdline_config = {};
+
+static void handle_options(int argc, char **argv)
+{
+	while (1) {
+		int option_idx = 0, c;
+		static const struct option long_options[] = {
+			{ "help", 0, 0, 'h' },
+			{ "debug", 1, 0, 'd' },
+			{ "daemonize", 0, 0, 'D' },
+			{ "config-file", 1, 0, 'c' },
+			{ "disable-color", 0, 0, 's' },
+			{ "timestamp", 0, 0, 'T' },
+			{ "version", 0, 0, 'V' },
+			{ "log-level", 1, 0, 'e' },
+			{}
+		};
+
+		c = getopt_long(argc, argv, "hc:d:Dc:sTVe:",
+				long_options, &option_idx);
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'h':
+			print_help();
+			exit(0);
+		case 's':
+			log_set_use_color(osmo_stderr_target, 0);
+			break;
+		case 'd':
+			log_parse_category_mask(osmo_stderr_target, optarg);
+			break;
+		case 'D':
+			cmdline_config.daemonize = 1;
+			break;
+		case 'c':
+			cmdline_config.config_file = optarg;
+			break;
+		case 'T':
+			log_set_print_timestamp(osmo_stderr_target, 1);
+			break;
+		case 'e':
+			log_set_log_level(osmo_stderr_target, atoi(optarg));
+			break;
+		case 'V':
+			print_version(1);
+			exit(0);
+			break;
+		default:
+			/* catch unknown options *as well as* missing arguments. */
+			fprintf(stderr, "Error in command line options. Exiting.\n");
+			exit(-1);
+		}
+	}
+}
+
+static int quit = 0;
+
+static void signal_handler(int signal)
+{
+	fprintf(stdout, "signal %u received\n", signal);
+
+	switch (signal) {
+	case SIGINT:
+	case SIGTERM:
+		quit++;
+		break;
+	case SIGABRT:
+		osmo_generate_backtrace();
+		/* in case of abort, we want to obtain a talloc report
+		 * and then return to the caller, who will abort the process */
+	case SIGUSR1:
+		talloc_report(tall_vty_ctx, stderr);
+		talloc_report_full(root_ctx, stderr);
+		break;
+	case SIGUSR2:
+		talloc_report_full(tall_vty_ctx, stderr);
+		break;
+	default:
+		break;
+	}
+}
+
+static struct vty_app_info vty_info = {
+	.name		= "tdef_vty_test",
+	.version	= PACKAGE_VERSION,
+};
+
+static const struct log_info_cat default_categories[] = {};
+
+const struct log_info log_info = {
+	.cat = default_categories,
+	.num_cat = ARRAY_SIZE(default_categories),
+};
+
+int main(int argc, char **argv)
+{
+	int rc;
+
+	root_ctx = talloc_named_const(NULL, 0, "tdef_vty_test");
+
+	osmo_init_logging2(root_ctx, &log_info);
+
+	vty_info.tall_ctx = root_ctx;
+	vty_init(&vty_info);
+	osmo_talloc_vty_add_cmds();
+
+	timer_init_vty(); /* <---- the only tdef relevant init */
+
+	handle_options(argc, argv);
+
+	if (cmdline_config.config_file) {
+		rc = vty_read_config_file(cmdline_config.config_file, NULL);
+		if (rc < 0) {
+			fprintf(stderr, "Failed to parse the config file: '%s'\n", cmdline_config.config_file);
+			return 1;
+		}
+	}
+
+	rc = telnet_init_dynif(root_ctx, NULL, vty_get_bind_addr(), 42042);
+	if (rc < 0)
+		return 2;
+
+	signal(SIGINT, &signal_handler);
+	signal(SIGTERM, &signal_handler);
+	signal(SIGABRT, &signal_handler);
+	signal(SIGUSR1, &signal_handler);
+	signal(SIGUSR2, &signal_handler);
+	osmo_init_ignore_signals();
+
+	if (cmdline_config.daemonize) {
+		rc = osmo_daemonize();
+		if (rc < 0) {
+			perror("Error during daemonize");
+			return 6;
+		}
+	}
+
+	while (!quit) {
+		log_reset_context();
+		osmo_select_main(0);
+	}
+
+	talloc_free(root_ctx);
+	talloc_free(tall_vty_ctx);
+
+	return 0;
+}
diff --git a/tests/tdef/tdef_vty_test_config_root.vty b/tests/tdef/tdef_vty_test_config_root.vty
new file mode 100644
index 0000000..12876a6
--- /dev/null
+++ b/tests/tdef/tdef_vty_test_config_root.vty
@@ -0,0 +1,292 @@
+tdef_vty_test> list
+...
+  show timer [(tea|test|software)] [TNNNN]
+...
+
+tdef_vty_test> show timer ?
+  [tea]       Tea time
+  [test]      Test timers
+  [software]  Typical software development cycle
+
+tdef_vty_test> show timer test ?
+  [TNNNN]  T-number, optionally preceded by 't' or 'T'.
+
+tdef_vty_test> show timer
+tea: T1 = 50 s	Water Boiling Timeout (default: 50 s)
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+tea: T3 = 5 m	Let tea cool down before drinking (default: 5 m)
+tea: T4 = 20 m	Forgot to drink tea while it's warm (default: 20 m)
+test: T1 = 100 s	Testing a hundred seconds (default: 100 s)
+test: T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+test: T3 = 100 m	Testing a hundred minutes (default: 100 m)
+test: T4 = 100	Testing a hundred potatoes (default: 100)
+test: T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+test: T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+software: T1 = 30 m	Write code (default: 30 m)
+software: T2 = 20 ms	Hit segfault (default: 20 ms)
+software: T3 = 480 m	Fix bugs (default: 480 m)
+
+tdef_vty_test> enable
+tdef_vty_test# show timer
+tea: T1 = 50 s	Water Boiling Timeout (default: 50 s)
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+tea: T3 = 5 m	Let tea cool down before drinking (default: 5 m)
+tea: T4 = 20 m	Forgot to drink tea while it's warm (default: 20 m)
+test: T1 = 100 s	Testing a hundred seconds (default: 100 s)
+test: T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+test: T3 = 100 m	Testing a hundred minutes (default: 100 m)
+test: T4 = 100	Testing a hundred potatoes (default: 100)
+test: T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+test: T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+software: T1 = 30 m	Write code (default: 30 m)
+software: T2 = 20 ms	Hit segfault (default: 20 ms)
+software: T3 = 480 m	Fix bugs (default: 480 m)
+
+tdef_vty_test# configure terminal
+
+tdef_vty_test(config)# show running-config
+... !timer
+
+tdef_vty_test(config)# list
+...
+  timer [(tea|test|software)] [TNNNN] [(<0-2147483647>|default)]
+...
+
+tdef_vty_test(config)# timer ?
+  [tea]       Tea time
+  [test]      Test timers
+  [software]  Typical software development cycle
+
+tdef_vty_test(config)# timer sof T123 ?
+  [<0-2147483647>]  New timer value
+  [default]         Set to default timer value
+
+tdef_vty_test(config)# timer sof T123 ?
+  [<0-2147483647>]  New timer value
+  [default]         Set to default timer value
+
+tdef_vty_test(config)# timer test ?
+  [TNNNN]  T-number, optionally preceded by 't' or 'T'.
+
+tdef_vty_test(config)# timer test t2 ?
+  [<0-2147483647>]  New timer value
+  [default]         Set to default timer value
+
+tdef_vty_test(config)# do show timer
+tea: T1 = 50 s	Water Boiling Timeout (default: 50 s)
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+tea: T3 = 5 m	Let tea cool down before drinking (default: 5 m)
+tea: T4 = 20 m	Forgot to drink tea while it's warm (default: 20 m)
+test: T1 = 100 s	Testing a hundred seconds (default: 100 s)
+test: T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+test: T3 = 100 m	Testing a hundred minutes (default: 100 m)
+test: T4 = 100	Testing a hundred potatoes (default: 100)
+test: T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+test: T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+software: T1 = 30 m	Write code (default: 30 m)
+software: T2 = 20 ms	Hit segfault (default: 20 ms)
+software: T3 = 480 m	Fix bugs (default: 480 m)
+
+tdef_vty_test(config)# do show timer tea
+tea: T1 = 50 s	Water Boiling Timeout (default: 50 s)
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+tea: T3 = 5 m	Let tea cool down before drinking (default: 5 m)
+tea: T4 = 20 m	Forgot to drink tea while it's warm (default: 20 m)
+
+tdef_vty_test(config)# do show timer tea 2
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+
+tdef_vty_test(config)# do show timer tea t2
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+
+tdef_vty_test(config)# do show timer tea T2
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+
+tdef_vty_test(config)# do show timer tea T5
+% No such timer: T5
+
+tdef_vty_test(config)# do show timer tea T0
+% No such timer: T0
+
+tdef_vty_test(config)# do show timer tea T-123
+% No such timer: T-123
+
+tdef_vty_test(config)# do show timer t
+tea: T1 = 50 s	Water Boiling Timeout (default: 50 s)
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+tea: T3 = 5 m	Let tea cool down before drinking (default: 5 m)
+tea: T4 = 20 m	Forgot to drink tea while it's warm (default: 20 m)
+test: T1 = 100 s	Testing a hundred seconds (default: 100 s)
+test: T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+test: T3 = 100 m	Testing a hundred minutes (default: 100 m)
+test: T4 = 100	Testing a hundred potatoes (default: 100)
+test: T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+test: T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+
+tdef_vty_test(config)# do show timer te
+tea: T1 = 50 s	Water Boiling Timeout (default: 50 s)
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+tea: T3 = 5 m	Let tea cool down before drinking (default: 5 m)
+tea: T4 = 20 m	Forgot to drink tea while it's warm (default: 20 m)
+test: T1 = 100 s	Testing a hundred seconds (default: 100 s)
+test: T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+test: T3 = 100 m	Testing a hundred minutes (default: 100 m)
+test: T4 = 100	Testing a hundred potatoes (default: 100)
+test: T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+test: T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+
+tdef_vty_test(config)# do show timer te T2
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+test: T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+
+
+tdef_vty_test(config)# timer tea 3 30
+tdef_vty_test(config)# timer tea T3
+tea: T3 = 30 m	Let tea cool down before drinking (default: 5 m)
+
+tdef_vty_test(config)# timer tea t3 31
+tdef_vty_test(config)# timer tea T3
+tea: T3 = 31 m	Let tea cool down before drinking (default: 5 m)
+
+tdef_vty_test(config)# timer tea T3 32
+tdef_vty_test(config)# timer tea T3
+tea: T3 = 32 m	Let tea cool down before drinking (default: 5 m)
+
+tdef_vty_test(config)# timer tea T-123 99
+% No such timer: T-123
+
+tdef_vty_test(config)# timer tea T0 0
+% No such timer: T0
+
+tdef_vty_test(config)# timer tea T123 default
+% No such timer: T123
+
+tdef_vty_test(config)# timer tea
+tea: T1 = 50 s	Water Boiling Timeout (default: 50 s)
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+tea: T3 = 32 m	Let tea cool down before drinking (default: 5 m)
+tea: T4 = 20 m	Forgot to drink tea while it's warm (default: 20 m)
+
+tdef_vty_test(config)# timer t
+tea: T1 = 50 s	Water Boiling Timeout (default: 50 s)
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+tea: T3 = 32 m	Let tea cool down before drinking (default: 5 m)
+tea: T4 = 20 m	Forgot to drink tea while it's warm (default: 20 m)
+test: T1 = 100 s	Testing a hundred seconds (default: 100 s)
+test: T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+test: T3 = 100 m	Testing a hundred minutes (default: 100 m)
+test: T4 = 100	Testing a hundred potatoes (default: 100)
+test: T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+test: T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+
+tdef_vty_test(config)# timer te T2
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+test: T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+
+tdef_vty_test(config)# timer test T2 100
+
+tdef_vty_test(config)# timer tes T2 100
+% Error: no timers found
+
+tdef_vty_test(config)# timer te T2 100
+% Error: no timers found
+
+
+tdef_vty_test(config)# do show timer software
+software: T1 = 30 m	Write code (default: 30 m)
+software: T2 = 20 ms	Hit segfault (default: 20 ms)
+software: T3 = 480 m	Fix bugs (default: 480 m)
+
+tdef_vty_test(config)# do show timer software 1
+software: T1 = 30 m	Write code (default: 30 m)
+
+tdef_vty_test(config)# do show timer software t1
+software: T1 = 30 m	Write code (default: 30 m)
+
+tdef_vty_test(config)# do show timer software T1
+software: T1 = 30 m	Write code (default: 30 m)
+
+tdef_vty_test(config)# do show timer software T99
+% No such timer: T99
+
+tdef_vty_test(config)# do show timer software T-123123
+% No such timer: T-123123
+
+tdef_vty_test(config)# do show timer software T0
+% No such timer: T0
+
+tdef_vty_test(config)# timer software 1 11
+tdef_vty_test(config)# timer software T1
+software: T1 = 11 m	Write code (default: 30 m)
+
+tdef_vty_test(config)# timer software t1 12
+tdef_vty_test(config)# timer software T1
+software: T1 = 12 m	Write code (default: 30 m)
+
+tdef_vty_test(config)# timer software T1 13
+tdef_vty_test(config)# timer software T2 0
+tdef_vty_test(config)# timer software
+software: T1 = 13 m	Write code (default: 30 m)
+software: T2 = 0 ms	Hit segfault (default: 20 ms)
+software: T3 = 480 m	Fix bugs (default: 480 m)
+
+tdef_vty_test(config)# timer softw
+software: T1 = 13 m	Write code (default: 30 m)
+software: T2 = 0 ms	Hit segfault (default: 20 ms)
+software: T3 = 480 m	Fix bugs (default: 480 m)
+
+tdef_vty_test(config)# timer softw T3
+software: T3 = 480 m	Fix bugs (default: 480 m)
+
+tdef_vty_test(config)# timer softw T3 23
+% Error: no timers found
+
+tdef_vty_test(config)# timer
+tea: T1 = 50 s	Water Boiling Timeout (default: 50 s)
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+tea: T3 = 32 m	Let tea cool down before drinking (default: 5 m)
+tea: T4 = 20 m	Forgot to drink tea while it's warm (default: 20 m)
+test: T1 = 100 s	Testing a hundred seconds (default: 100 s)
+test: T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+test: T3 = 100 m	Testing a hundred minutes (default: 100 m)
+test: T4 = 100	Testing a hundred potatoes (default: 100)
+test: T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+test: T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+software: T1 = 13 m	Write code (default: 30 m)
+software: T2 = 0 ms	Hit segfault (default: 20 ms)
+software: T3 = 480 m	Fix bugs (default: 480 m)
+
+tdef_vty_test(config)# do show timer
+tea: T1 = 50 s	Water Boiling Timeout (default: 50 s)
+tea: T2 = 300 s	Tea brewing (default: 300 s)
+tea: T3 = 32 m	Let tea cool down before drinking (default: 5 m)
+tea: T4 = 20 m	Forgot to drink tea while it's warm (default: 20 m)
+test: T1 = 100 s	Testing a hundred seconds (default: 100 s)
+test: T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+test: T3 = 100 m	Testing a hundred minutes (default: 100 m)
+test: T4 = 100	Testing a hundred potatoes (default: 100)
+test: T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+test: T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+software: T1 = 13 m	Write code (default: 30 m)
+software: T2 = 0 ms	Hit segfault (default: 20 ms)
+software: T3 = 480 m	Fix bugs (default: 480 m)
+
+tdef_vty_test(config)# show running-config
+... !timer
+timer tea T3 32
+timer software T1 13
+timer software T2 0
+... !timer
+
+tdef_vty_test(config)# timer tea T3 default
+tdef_vty_test(config)# timer software T1 default
+tdef_vty_test(config)# show running-config
+... !timer
+timer software T2 0
+... !timer
+
+tdef_vty_test(config)# timer softw 2 default
+% Error: no timers found
+tdef_vty_test(config)# timer software 2 default
+tdef_vty_test(config)# show running-config
+... !timer
diff --git a/tests/tdef/tdef_vty_test_config_subnode.c b/tests/tdef/tdef_vty_test_config_subnode.c
new file mode 100644
index 0000000..c371c8d
--- /dev/null
+++ b/tests/tdef/tdef_vty_test_config_subnode.c
@@ -0,0 +1,288 @@
+/* Test implementation for osmo_tdef VTY configuration API. */
+/*
+ * (C) 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * Author: Neels Hofmeyr <nhofmeyr@sysmocom.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#define _GNU_SOURCE
+#include <getopt.h>
+#include <signal.h>
+#include <limits.h>
+#include <string.h>
+
+#include <osmocom/core/application.h>
+
+#include <osmocom/vty/command.h>
+#include <osmocom/vty/misc.h>
+#include <osmocom/vty/telnet_interface.h>
+
+#include <osmocom/core/tdef.h>
+#include <osmocom/vty/tdef_vty.h>
+
+#include <stdlib.h>
+
+#include "config.h"
+
+/* ------------------- HERE IS THE INTERESTING TDEF RELEVANT PART ------------------- */
+
+/* This example keeps a single global timer group and offers a custom 'timer' VTY command in a 'network' subnode below
+ * the CONFIG_NODE.
+ * the tdef_vty_test_config_subnode.vty transcript test.
+ */
+
+static struct osmo_tdef global_tdefs[] = {
+	{ .T=1, .default_val=100, .desc="Testing a hundred seconds" },  // default is .unit=OSMO_TDEF_S == 0
+	{ .T=2, .default_val=100, .unit=OSMO_TDEF_MS, .desc="Testing a hundred milliseconds" },
+	{ .T=3, .default_val=100, .unit=OSMO_TDEF_M, .desc="Testing a hundred minutes" },
+	{ .T=4, .default_val=100, .unit=OSMO_TDEF_CUSTOM, .desc="Testing a hundred potatoes" },
+	{ .T=INT_MAX, .default_val=ULONG_MAX, .unit=OSMO_TDEF_M, .desc="Very large" },
+	{ .T=-23, .default_val=-15, .desc="Negative T number" },
+	{}  //  <-- important! last entry shall be zero
+};
+
+enum tdef_vty_test_nodes {
+	GSMNET_NODE = _LAST_OSMOVTY_NODE + 1,
+};
+
+/* This example offers 'timer T123' commands within an "unrelated" already existing subnode. */
+static struct cmd_node gsmnet_node = {
+	GSMNET_NODE,
+	"%s(config-net)# ",
+	1,
+};
+
+DEFUN(show_timer, show_timer_cmd,
+      "show timer " OSMO_TDEF_VTY_ARG_T_OPTIONAL,
+      SHOW_STR "Show timers\n"
+      OSMO_TDEF_VTY_DOC_T)
+{
+	const char *T_arg = argc > 0 ? argv[0] : NULL;
+	return osmo_tdef_vty_show_cmd(vty, global_tdefs, T_arg, NULL);
+}
+
+DEFUN(cfg_net_timer, cfg_net_timer_cmd,
+      "timer " OSMO_TDEF_VTY_ARG_SET_OPTIONAL,
+      "Configure or show timers\n"
+      OSMO_TDEF_VTY_DOC_SET)
+{
+	/* If any arguments are missing, redirect to 'show' */
+	if (argc < 2)
+		return show_timer(self, vty, argc, argv);
+	return osmo_tdef_vty_set_cmd(vty, global_tdefs, argv);
+}
+
+DEFUN(cfg_net, cfg_net_cmd,
+      "network", "Enter network node\n")
+{
+	vty->node = GSMNET_NODE;
+	return CMD_SUCCESS;
+}
+
+static int config_write_gsmnet(struct vty *vty)
+{
+	vty_out(vty, "net%s", VTY_NEWLINE);
+	/* usually, here would be the output of any other 'net' config items... */
+
+	osmo_tdef_vty_write(vty, global_tdefs, " timer ");
+	return CMD_SUCCESS;
+}
+
+static void gsmnet_init_vty()
+{
+	install_node(&gsmnet_node, config_write_gsmnet);
+	install_element(CONFIG_NODE, &cfg_net_cmd);
+
+	osmo_tdefs_reset(global_tdefs);
+	install_element_ve(&show_timer_cmd);
+	install_element(GSMNET_NODE, &cfg_net_timer_cmd);
+}
+
+/* ------------------- THE REST is just boilerplate osmo main() ------------------- */
+
+void *root_ctx = NULL;
+
+static void print_help()
+{
+	printf( "options:\n"
+		"  -h	--help		this text\n"
+		"  -d	--debug MASK	Enable debugging (e.g. -d DRSL:DOML:DLAPDM)\n"
+		"  -D	--daemonize	For the process into a background daemon\n"
+		"  -c	--config-file	Specify the filename of the config file\n"
+		"  -s	--disable-color	Don't use colors in stderr log output\n"
+		"  -T	--timestamp	Prefix every log line with a timestamp\n"
+		"  -V	--version	Print version information and exit\n"
+		"  -e	--log-level	Set a global log-level\n"
+		);
+}
+
+static struct {
+	const char *config_file;
+	int daemonize;
+} cmdline_config = {};
+
+static void handle_options(int argc, char **argv)
+{
+	while (1) {
+		int option_idx = 0, c;
+		static const struct option long_options[] = {
+			{ "help", 0, 0, 'h' },
+			{ "debug", 1, 0, 'd' },
+			{ "daemonize", 0, 0, 'D' },
+			{ "config-file", 1, 0, 'c' },
+			{ "disable-color", 0, 0, 's' },
+			{ "timestamp", 0, 0, 'T' },
+			{ "version", 0, 0, 'V' },
+			{ "log-level", 1, 0, 'e' },
+			{}
+		};
+
+		c = getopt_long(argc, argv, "hc:d:Dc:sTVe:",
+				long_options, &option_idx);
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'h':
+			print_help();
+			exit(0);
+		case 's':
+			log_set_use_color(osmo_stderr_target, 0);
+			break;
+		case 'd':
+			log_parse_category_mask(osmo_stderr_target, optarg);
+			break;
+		case 'D':
+			cmdline_config.daemonize = 1;
+			break;
+		case 'c':
+			cmdline_config.config_file = optarg;
+			break;
+		case 'T':
+			log_set_print_timestamp(osmo_stderr_target, 1);
+			break;
+		case 'e':
+			log_set_log_level(osmo_stderr_target, atoi(optarg));
+			break;
+		case 'V':
+			print_version(1);
+			exit(0);
+			break;
+		default:
+			/* catch unknown options *as well as* missing arguments. */
+			fprintf(stderr, "Error in command line options. Exiting.\n");
+			exit(-1);
+		}
+	}
+}
+
+static int quit = 0;
+
+static void signal_handler(int signal)
+{
+	fprintf(stdout, "signal %u received\n", signal);
+
+	switch (signal) {
+	case SIGINT:
+	case SIGTERM:
+		quit++;
+		break;
+	case SIGABRT:
+		osmo_generate_backtrace();
+		/* in case of abort, we want to obtain a talloc report
+		 * and then return to the caller, who will abort the process */
+	case SIGUSR1:
+		talloc_report(tall_vty_ctx, stderr);
+		talloc_report_full(root_ctx, stderr);
+		break;
+	case SIGUSR2:
+		talloc_report_full(tall_vty_ctx, stderr);
+		break;
+	default:
+		break;
+	}
+}
+
+static struct vty_app_info vty_info = {
+	.name		= "tdef_vty_test",
+	.version	= PACKAGE_VERSION,
+};
+
+static const struct log_info_cat default_categories[] = {};
+
+const struct log_info log_info = {
+	.cat = default_categories,
+	.num_cat = ARRAY_SIZE(default_categories),
+};
+
+int main(int argc, char **argv)
+{
+	int rc;
+
+	root_ctx = talloc_named_const(NULL, 0, "tdef_vty_test");
+
+	osmo_init_logging2(root_ctx, &log_info);
+
+	vty_info.tall_ctx = root_ctx;
+	vty_init(&vty_info);
+	osmo_talloc_vty_add_cmds();
+
+	gsmnet_init_vty(); /* <--- relevant init for this example */
+
+	handle_options(argc, argv);
+
+	if (cmdline_config.config_file) {
+		rc = vty_read_config_file(cmdline_config.config_file, NULL);
+		if (rc < 0) {
+			fprintf(stderr, "Failed to parse the config file: '%s'\n", cmdline_config.config_file);
+			return 1;
+		}
+	}
+
+	rc = telnet_init_dynif(root_ctx, NULL, vty_get_bind_addr(), 42042);
+	if (rc < 0)
+		return 2;
+
+	signal(SIGINT, &signal_handler);
+	signal(SIGTERM, &signal_handler);
+	signal(SIGABRT, &signal_handler);
+	signal(SIGUSR1, &signal_handler);
+	signal(SIGUSR2, &signal_handler);
+	osmo_init_ignore_signals();
+
+	if (cmdline_config.daemonize) {
+		rc = osmo_daemonize();
+		if (rc < 0) {
+			perror("Error during daemonize");
+			return 6;
+		}
+	}
+
+	while (!quit) {
+		log_reset_context();
+		osmo_select_main(0);
+	}
+
+	talloc_free(root_ctx);
+	talloc_free(tall_vty_ctx);
+
+	return 0;
+}
diff --git a/tests/tdef/tdef_vty_test_config_subnode.vty b/tests/tdef/tdef_vty_test_config_subnode.vty
new file mode 100644
index 0000000..6cfd3bf
--- /dev/null
+++ b/tests/tdef/tdef_vty_test_config_subnode.vty
@@ -0,0 +1,107 @@
+tdef_vty_test> list
+... !timer
+  show timer [TNNNN]
+... !timer
+
+tdef_vty_test> show timer ?
+  [TNNNN]  T-number, optionally preceded by 't' or 'T'.
+
+tdef_vty_test> show timer
+T1 = 100 s	Testing a hundred seconds (default: 100 s)
+T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+T3 = 100 m	Testing a hundred minutes (default: 100 m)
+T4 = 100	Testing a hundred potatoes (default: 100)
+T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+
+tdef_vty_test> enable
+tdef_vty_test# show timer
+T1 = 100 s	Testing a hundred seconds (default: 100 s)
+T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+T3 = 100 m	Testing a hundred minutes (default: 100 m)
+T4 = 100	Testing a hundred potatoes (default: 100)
+T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+
+tdef_vty_test# configure terminal
+tdef_vty_test(config)# show running-config
+... !timer
+
+tdef_vty_test(config)# network
+
+tdef_vty_test(config-net)# do show timer
+T1 = 100 s	Testing a hundred seconds (default: 100 s)
+T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+T3 = 100 m	Testing a hundred minutes (default: 100 m)
+T4 = 100	Testing a hundred potatoes (default: 100)
+T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+T-23 = 18446744073709551601 s	Negative T number (default: 18446744073709551601 s)
+
+tdef_vty_test(config-net)# do show timer T3
+T3 = 100 m	Testing a hundred minutes (default: 100 m)
+tdef_vty_test(config-net)# do show timer 3
+T3 = 100 m	Testing a hundred minutes (default: 100 m)
+tdef_vty_test(config-net)# do show timer t3
+T3 = 100 m	Testing a hundred minutes (default: 100 m)
+
+tdef_vty_test(config-net)# timer T1 5
+tdef_vty_test(config-net)# timer T1
+T1 = 5 s	Testing a hundred seconds (default: 100 s)
+
+tdef_vty_test(config-net)# timer t1 678
+tdef_vty_test(config-net)# timer T1
+T1 = 678 s	Testing a hundred seconds (default: 100 s)
+
+tdef_vty_test(config-net)# timer 1 9012345
+tdef_vty_test(config-net)# timer T1
+T1 = 9012345 s	Testing a hundred seconds (default: 100 s)
+
+tdef_vty_test(config-net)# do show timer T666
+% No such timer: T666
+tdef_vty_test(config-net)# do show timer t666
+% No such timer: T666
+tdef_vty_test(config-net)# do show timer 666
+% No such timer: T666
+
+tdef_vty_test(config-net)# timer T666
+% No such timer: T666
+tdef_vty_test(config-net)# timer t666
+% No such timer: T666
+tdef_vty_test(config-net)# timer 666
+% No such timer: T666
+
+tdef_vty_test(config-net)# timer T666 5
+% No such timer: T666
+
+tdef_vty_test(config-net)# timer T-23 42
+tdef_vty_test(config-net)# timer T-23
+T-23 = 42 s	Negative T number (default: 18446744073709551601 s)
+
+tdef_vty_test(config-net)# timer t-23 43
+tdef_vty_test(config-net)# timer T-23
+T-23 = 43 s	Negative T number (default: 18446744073709551601 s)
+
+tdef_vty_test(config-net)# timer -23 44
+tdef_vty_test(config-net)# timer T-23
+T-23 = 44 s	Negative T number (default: 18446744073709551601 s)
+
+tdef_vty_test(config-net)# do show timer
+T1 = 9012345 s	Testing a hundred seconds (default: 100 s)
+T2 = 100 ms	Testing a hundred milliseconds (default: 100 ms)
+T3 = 100 m	Testing a hundred minutes (default: 100 m)
+T4 = 100	Testing a hundred potatoes (default: 100)
+T2147483647 = 18446744073709551615 m	Very large (default: 18446744073709551615 m)
+T-23 = 44 s	Negative T number (default: 18446744073709551601 s)
+
+tdef_vty_test(config-net)# show running-config
+... !timer
+net
+ timer T1 9012345
+ timer T-23 44
+... !timer
+
+tdef_vty_test(config-net)# timer T1 default
+tdef_vty_test(config-net)# timer T-23 default
+
+tdef_vty_test(config-net)# show running-config
+... !timer
diff --git a/tests/tdef/tdef_vty_test_dynamic.c b/tests/tdef/tdef_vty_test_dynamic.c
new file mode 100644
index 0000000..20dae53
--- /dev/null
+++ b/tests/tdef/tdef_vty_test_dynamic.c
@@ -0,0 +1,362 @@
+/* Test implementation for osmo_tdef VTY configuration API. */
+/*
+ * (C) 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * Author: Neels Hofmeyr <nhofmeyr@sysmocom.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#define _GNU_SOURCE
+#include <getopt.h>
+#include <signal.h>
+#include <limits.h>
+#include <string.h>
+
+#include <osmocom/core/application.h>
+
+#include <osmocom/vty/command.h>
+#include <osmocom/vty/misc.h>
+#include <osmocom/vty/telnet_interface.h>
+
+#include <osmocom/core/tdef.h>
+#include <osmocom/vty/tdef_vty.h>
+
+#include <stdlib.h>
+
+#include "config.h"
+
+void *root_ctx = NULL;
+
+/* ------------------- HERE IS THE INTERESTING TDEF RELEVANT PART ------------------- */
+
+/* This example keeps a separate list of timers for each instance of a dynamically allocated instance of a VTY node,
+ * for example of keeping separate timers for each BTS in a BSC.
+ */
+
+static const struct osmo_tdef bts_default_tdefs[] = {
+	{ .T=1111, .default_val=2, .desc="Dynamic Duo" },
+	{ .T=2222, .default_val=1, .desc="BATMAN" },
+	{ .T=3333, .default_val=12, .desc="Dadadadadadadadadadadada" },
+	{ .T=4444, .default_val=500, .unit=OSMO_TDEF_MS, .desc="POW!" },
+	{}
+};
+
+
+/* Boilerplate dynamic VTY node ... */
+
+enum tdef_vty_test_nodes {
+	MEMBER_NODE = _LAST_OSMOVTY_NODE + 1,
+};
+
+static struct cmd_node member_node = {
+	MEMBER_NODE,
+	"%s(config-member)# ",
+	1,
+};
+
+struct member {
+	struct llist_head entry;
+	char name[23];
+	struct osmo_tdef *tdefs;
+};
+
+LLIST_HEAD(all_members);
+
+struct member *member_alloc(const char *name)
+{
+	struct member *m = talloc_zero(root_ctx, struct member);
+	osmo_strlcpy(m->name, name, sizeof(m->name));
+
+	/* DYNAMIC TDEF COPIES */
+	m->tdefs = (struct osmo_tdef*)talloc_size(m, sizeof(bts_default_tdefs));
+	memcpy((char*)m->tdefs, (char*)&bts_default_tdefs, sizeof(bts_default_tdefs));
+	osmo_tdefs_reset(m->tdefs);
+
+	llist_add_tail(&m->entry, &all_members);
+	return m;
+}
+
+struct member *member_find(const char *name)
+{
+	struct member *m;
+	llist_for_each_entry(m, &all_members, entry) {
+		if (!strcmp(m->name, name))
+			return m;
+	}
+	return NULL;
+}
+
+DEFUN(cfg_member, cfg_member_cmd,
+      "member NAME",
+      "Enter member node\n" "Existing or new member node name\n")
+{
+	const char *name = argv[0];
+	struct member *m = member_find(name);
+	if (!m)
+		m = member_alloc(name);
+	vty->index = m;
+	vty->node = MEMBER_NODE;
+	return CMD_SUCCESS;
+}
+
+
+/* TDEF SPECIFIC VTY */
+
+static bool startswith(const char *str, const char *startswith_str)
+{
+	if (!startswith_str)
+		return true;
+	if (!str)
+		return false;
+	return strncmp(str, startswith_str, strlen(startswith_str)) == 0;
+}
+
+DEFUN(show_timer, show_member_timer_cmd,
+      "show member-timer [NAME] " OSMO_TDEF_VTY_ARG_T_OPTIONAL,
+      SHOW_STR "Show timers for a specific member" "member name\n"
+      OSMO_TDEF_VTY_DOC_T)
+{
+	const char *name = argc > 0 ? argv[0] : NULL;
+	struct member *m;
+	const char *T_arg = argc > 1 ? argv[1] : NULL;
+	int shown = 0;
+
+	llist_for_each_entry(m, &all_members, entry) {
+		if (!name || startswith(m->name, name)) {
+			osmo_tdef_vty_show_cmd(vty, m->tdefs, T_arg, "%11s: ", m->name);
+			shown ++;
+		}
+	}
+	if (!shown) {
+		vty_out(vty, "%% No such member: %s%s", name ? : "(none)", VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_member_timer, cfg_member_timer_cmd,
+      "timer " OSMO_TDEF_VTY_ARG_SET_OPTIONAL,
+      "Configure or show timers for this member\n"
+      OSMO_TDEF_VTY_DOC_SET)
+{
+	struct member *m = vty->index;
+
+	if (!m || !m->tdefs) {
+		vty_out(vty, "%% No timers here%s", VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	/* If any arguments are missing, redirect to 'show' */
+	if (argc < 2) {
+		const char *T_arg = argc > 0 ? argv[0] : NULL;
+		return osmo_tdef_vty_show_cmd(vty, m->tdefs, T_arg, "%11s: ", m->name);
+	}
+
+	return osmo_tdef_vty_set_cmd(vty, m->tdefs, argv);
+}
+
+static int config_write_member(struct vty *vty)
+{
+	struct member *m;
+	llist_for_each_entry(m, &all_members, entry) {
+		vty_out(vty, "member %s%s", m->name, VTY_NEWLINE);
+		osmo_tdef_vty_write(vty, m->tdefs, " timer ");
+	}
+
+	return CMD_SUCCESS;
+}
+
+static void member_init_vty()
+{
+	install_node(&member_node, config_write_member);
+	install_element(CONFIG_NODE, &cfg_member_cmd);
+
+	install_element_ve(&show_member_timer_cmd);
+	install_element(MEMBER_NODE, &cfg_member_timer_cmd);
+}
+
+/* ------------------- THE REST is just boilerplate osmo main() ------------------- */
+
+static void print_help()
+{
+	printf( "options:\n"
+		"  -h	--help		this text\n"
+		"  -d	--debug MASK	Enable debugging (e.g. -d DRSL:DOML:DLAPDM)\n"
+		"  -D	--daemonize	For the process into a background daemon\n"
+		"  -c	--config-file	Specify the filename of the config file\n"
+		"  -s	--disable-color	Don't use colors in stderr log output\n"
+		"  -T	--timestamp	Prefix every log line with a timestamp\n"
+		"  -V	--version	Print version information and exit\n"
+		"  -e	--log-level	Set a global log-level\n"
+		);
+}
+
+static struct {
+	const char *config_file;
+	int daemonize;
+} cmdline_config = {};
+
+static void handle_options(int argc, char **argv)
+{
+	while (1) {
+		int option_idx = 0, c;
+		static const struct option long_options[] = {
+			{ "help", 0, 0, 'h' },
+			{ "debug", 1, 0, 'd' },
+			{ "daemonize", 0, 0, 'D' },
+			{ "config-file", 1, 0, 'c' },
+			{ "disable-color", 0, 0, 's' },
+			{ "timestamp", 0, 0, 'T' },
+			{ "version", 0, 0, 'V' },
+			{ "log-level", 1, 0, 'e' },
+			{}
+		};
+
+		c = getopt_long(argc, argv, "hc:d:Dc:sTVe:",
+				long_options, &option_idx);
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'h':
+			print_help();
+			exit(0);
+		case 's':
+			log_set_use_color(osmo_stderr_target, 0);
+			break;
+		case 'd':
+			log_parse_category_mask(osmo_stderr_target, optarg);
+			break;
+		case 'D':
+			cmdline_config.daemonize = 1;
+			break;
+		case 'c':
+			cmdline_config.config_file = optarg;
+			break;
+		case 'T':
+			log_set_print_timestamp(osmo_stderr_target, 1);
+			break;
+		case 'e':
+			log_set_log_level(osmo_stderr_target, atoi(optarg));
+			break;
+		case 'V':
+			print_version(1);
+			exit(0);
+			break;
+		default:
+			/* catch unknown options *as well as* missing arguments. */
+			fprintf(stderr, "Error in command line options. Exiting.\n");
+			exit(-1);
+		}
+	}
+}
+
+static int quit = 0;
+
+static void signal_handler(int signal)
+{
+	fprintf(stdout, "signal %u received\n", signal);
+
+	switch (signal) {
+	case SIGINT:
+	case SIGTERM:
+		quit++;
+		break;
+	case SIGABRT:
+		osmo_generate_backtrace();
+		/* in case of abort, we want to obtain a talloc report
+		 * and then return to the caller, who will abort the process */
+	case SIGUSR1:
+		talloc_report(tall_vty_ctx, stderr);
+		talloc_report_full(root_ctx, stderr);
+		break;
+	case SIGUSR2:
+		talloc_report_full(tall_vty_ctx, stderr);
+		break;
+	default:
+		break;
+	}
+}
+
+static struct vty_app_info vty_info = {
+	.name		= "tdef_vty_test",
+	.version	= PACKAGE_VERSION,
+};
+
+static const struct log_info_cat default_categories[] = {};
+
+const struct log_info log_info = {
+	.cat = default_categories,
+	.num_cat = ARRAY_SIZE(default_categories),
+};
+
+int main(int argc, char **argv)
+{
+	int rc;
+
+	root_ctx = talloc_named_const(NULL, 0, "tdef_vty_test");
+
+	osmo_init_logging2(root_ctx, &log_info);
+
+	vty_info.tall_ctx = root_ctx;
+	vty_init(&vty_info);
+	osmo_talloc_vty_add_cmds();
+
+	member_init_vty(); /* <--- relevant init for this example */
+
+	handle_options(argc, argv);
+
+	if (cmdline_config.config_file) {
+		rc = vty_read_config_file(cmdline_config.config_file, NULL);
+		if (rc < 0) {
+			fprintf(stderr, "Failed to parse the config file: '%s'\n", cmdline_config.config_file);
+			return 1;
+		}
+	}
+
+	rc = telnet_init_dynif(root_ctx, NULL, vty_get_bind_addr(), 42042);
+	if (rc < 0)
+		return 2;
+
+	signal(SIGINT, &signal_handler);
+	signal(SIGTERM, &signal_handler);
+	signal(SIGABRT, &signal_handler);
+	signal(SIGUSR1, &signal_handler);
+	signal(SIGUSR2, &signal_handler);
+	osmo_init_ignore_signals();
+
+	if (cmdline_config.daemonize) {
+		rc = osmo_daemonize();
+		if (rc < 0) {
+			perror("Error during daemonize");
+			return 6;
+		}
+	}
+
+	while (!quit) {
+		log_reset_context();
+		osmo_select_main(0);
+	}
+
+	talloc_free(root_ctx);
+	talloc_free(tall_vty_ctx);
+
+	return 0;
+}
diff --git a/tests/tdef/tdef_vty_test_dynamic.vty b/tests/tdef/tdef_vty_test_dynamic.vty
new file mode 100644
index 0000000..6aae746
--- /dev/null
+++ b/tests/tdef/tdef_vty_test_dynamic.vty
@@ -0,0 +1,83 @@
+tdef_vty_test> list
+...
+  show member-timer [NAME] [TNNNN]
+...
+
+tdef_vty_test> enable
+tdef_vty_test# configure terminal
+
+tdef_vty_test(config)# member robin
+tdef_vty_test(config-member)# timer
+      robin: T1111 = 2 s	Dynamic Duo (default: 2 s)
+      robin: T2222 = 1 s	BATMAN (default: 1 s)
+      robin: T3333 = 12 s	Dadadadadadadadadadadada (default: 12 s)
+      robin: T4444 = 500 ms	POW! (default: 500 ms)
+
+tdef_vty_test(config-member)# timer T2222 423
+tdef_vty_test(config-member)# timer T2222
+      robin: T2222 = 423 s	BATMAN (default: 1 s)
+
+tdef_vty_test(config-member)# timer
+      robin: T1111 = 2 s	Dynamic Duo (default: 2 s)
+      robin: T2222 = 423 s	BATMAN (default: 1 s)
+      robin: T3333 = 12 s	Dadadadadadadadadadadada (default: 12 s)
+      robin: T4444 = 500 ms	POW! (default: 500 ms)
+
+tdef_vty_test(config-member)# do show member-timer
+      robin: T1111 = 2 s	Dynamic Duo (default: 2 s)
+      robin: T2222 = 423 s	BATMAN (default: 1 s)
+      robin: T3333 = 12 s	Dadadadadadadadadadadada (default: 12 s)
+      robin: T4444 = 500 ms	POW! (default: 500 ms)
+
+tdef_vty_test(config-member)# exit
+
+tdef_vty_test(config)# member batman
+tdef_vty_test(config-member)# timer 3333 17
+tdef_vty_test(config-member)# timer 3333
+     batman: T3333 = 17 s	Dadadadadadadadadadadada (default: 12 s)
+
+tdef_vty_test(config-member)# show running-config
+
+Current configuration:
+...
+member robin
+ timer T2222 423
+member batman
+ timer T3333 17
+...
+
+tdef_vty_test(config-member)# timer 3333 default
+
+tdef_vty_test(config-member)# show running-config
+...
+member robin
+ timer T2222 423
+member batman
+... !timer
+
+tdef_vty_test(config-member)# exit
+tdef_vty_test(config)# exit
+tdef_vty_test# show member-timer
+      robin: T1111 = 2 s	Dynamic Duo (default: 2 s)
+      robin: T2222 = 423 s	BATMAN (default: 1 s)
+      robin: T3333 = 12 s	Dadadadadadadadadadadada (default: 12 s)
+      robin: T4444 = 500 ms	POW! (default: 500 ms)
+     batman: T1111 = 2 s	Dynamic Duo (default: 2 s)
+     batman: T2222 = 1 s	BATMAN (default: 1 s)
+     batman: T3333 = 12 s	Dadadadadadadadadadadada (default: 12 s)
+     batman: T4444 = 500 ms	POW! (default: 500 ms)
+
+tdef_vty_test# show member-timer batman
+     batman: T1111 = 2 s	Dynamic Duo (default: 2 s)
+     batman: T2222 = 1 s	BATMAN (default: 1 s)
+     batman: T3333 = 12 s	Dadadadadadadadadadadada (default: 12 s)
+     batman: T4444 = 500 ms	POW! (default: 500 ms)
+
+tdef_vty_test# show member-timer robin
+      robin: T1111 = 2 s	Dynamic Duo (default: 2 s)
+      robin: T2222 = 423 s	BATMAN (default: 1 s)
+      robin: T3333 = 12 s	Dadadadadadadadadadadada (default: 12 s)
+      robin: T4444 = 500 ms	POW! (default: 500 ms)
+
+tdef_vty_test# show member-timer joker
+% No such member: joker
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 6aaaa78..0093403 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -325,3 +325,9 @@
 cat $abs_srcdir/gsm23003/gsm23003_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/gsm23003/gsm23003_test], [0], [expout], [ignore])
 AT_CLEANUP
+
+AT_SETUP([tdef])
+AT_KEYWORDS([tdef])
+cat $abs_srcdir/tdef/tdef_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/tdef/tdef_test], [0], [expout], [ignore])
+AT_CLEANUP