diff --git a/tests/Makefile.am b/tests/Makefile.am
index b72619f..c44b6f0 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -42,6 +42,7 @@
 		 bsslap/bsslap_test					\
 		 bssmap_le/bssmap_le_test				\
 		 it_q/it_q_test						\
+		 time_cc/time_cc_test					\
 		 gsm48/rest_octets_test					\
 		 base64/base64_test					\
 		 $(NULL)
@@ -324,6 +325,9 @@
 it_q_it_q_test_SOURCES = it_q/it_q_test.c
 it_q_it_q_test_LDADD = $(LDADD)
 
+time_cc_time_cc_test_SOURCES = time_cc/time_cc_test.c
+time_cc_time_cc_test_LDADD = $(LDADD)
+
 # The `:;' works around a Bash 3.2 bug when the output is not writeable.
 $(srcdir)/package.m4: $(top_srcdir)/configure.ac
 	:;{ \
@@ -413,6 +417,7 @@
 	     bsslap/bsslap_test.ok \
 	     bssmap_le/bssmap_le_test.ok \
 	     it_q/it_q_test.ok \
+	     time_cc/time_cc_test.ok \
 	     gsm48/rest_octets_test.ok \
 	     base64/base64_test.ok \
 	     $(NULL)
@@ -609,6 +614,8 @@
 		>$(srcdir)/bssmap_le/bssmap_le_test.ok
 	it_q/it_q_test \
 		>$(srcdir)/it_q/it_q_test.ok
+	time_cc/time_cc_test \
+		>$(srcdir)/time_cc/time_cc_test.ok
 
 check-local: atconfig $(TESTSUITE)
 	[ -e /proc/cpuinfo ] && cat /proc/cpuinfo
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 6ac5970..975b51e 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -452,3 +452,9 @@
 cat $abs_srcdir/base64/base64_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/base64/base64_test], [0], [expout], [ignore])
 AT_CLEANUP
+
+AT_SETUP([time_cc])
+AT_KEYWORDS([time_cc])
+cat $abs_srcdir/time_cc/time_cc_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/time_cc/time_cc_test], [0], [expout], [ignore])
+AT_CLEANUP
diff --git a/tests/time_cc/time_cc_test.c b/tests/time_cc/time_cc_test.c
new file mode 100644
index 0000000..22ea7f6
--- /dev/null
+++ b/tests/time_cc/time_cc_test.c
@@ -0,0 +1,768 @@
+/* (C) 2021 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ * All Rights Reserved
+ *
+ * Author: Neels Janosch Hofmeyr <nhofmeyr@sysmocom.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <inttypes.h>
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/rate_ctr.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/core/application.h>
+#include <osmocom/core/select.h>
+#include <osmocom/core/tdef.h>
+#include <osmocom/core/time_cc.h>
+
+enum my_ctrs {
+	CTR_CEIL,
+	CTR_ROUND,
+	CTR_FLOOR,
+};
+
+const struct rate_ctr_desc my_ctr_desc[] = {
+	[CTR_CEIL] =	{"ceil", "testing round_threshold_usec = 1"},
+	[CTR_ROUND] =	{"round", "testing round_threshold_usec = 0 = gran_usec/2"},
+	[CTR_FLOOR] =	{"floor", "testing round_threshold_usec = gran_usec"},
+};
+
+const struct rate_ctr_group_desc my_ctrg_desc = {
+	"time_cc_test",
+	"Counters for osmo_time_cc test",
+	0,
+	ARRAY_SIZE(my_ctr_desc),
+	my_ctr_desc,
+};
+
+struct rate_ctr_group *my_ctrg;
+
+
+enum my_obj_timers {
+	T_GRAN = -23,
+	T_ROUND_THRESH = -24,
+	T_FORGET_SUM = -25,
+};
+
+struct osmo_tdef g_my_obj_tdefs[] = {
+	{ .T = T_GRAN, .default_val = 0, .unit = OSMO_TDEF_MS, .desc = "flag_cc granularity, or zero for 1 second" },
+	{ .T = T_ROUND_THRESH, .default_val = 0, .unit = OSMO_TDEF_MS,
+		.desc = "flag_cc rounding threshold, or zero for half a granularity" },
+	{ .T = T_FORGET_SUM, .default_val = 0, .unit = OSMO_TDEF_MS,
+		.desc = "flag_cc inactivity forget period, or zero to not forget any timings" },
+	{}
+};
+
+
+struct my_obj {
+	struct osmo_time_cc flag_cc_ceil;
+	struct osmo_time_cc flag_cc_round;
+	struct osmo_time_cc flag_cc_floor;
+};
+
+void my_obj_init(struct my_obj *my_obj)
+{
+	osmo_time_cc_init(&my_obj->flag_cc_ceil);
+	my_obj->flag_cc_ceil.cfg = (struct osmo_time_cc_cfg){
+		.rate_ctr = rate_ctr_group_get_ctr(my_ctrg, CTR_CEIL),
+		.round_threshold_usec = 1,
+		.T_gran = T_GRAN,
+		.T_forget_sum = T_FORGET_SUM,
+		.T_defs = g_my_obj_tdefs,
+	};
+
+	osmo_time_cc_init(&my_obj->flag_cc_round);
+	my_obj->flag_cc_round.cfg = (struct osmo_time_cc_cfg){
+		.rate_ctr = rate_ctr_group_get_ctr(my_ctrg, CTR_ROUND),
+		.T_gran = T_GRAN,
+		.T_round_threshold = T_ROUND_THRESH,
+		.T_forget_sum = T_FORGET_SUM,
+		.T_defs = g_my_obj_tdefs,
+	};
+
+	osmo_time_cc_init(&my_obj->flag_cc_floor);
+	my_obj->flag_cc_floor.cfg = (struct osmo_time_cc_cfg){
+		.rate_ctr = rate_ctr_group_get_ctr(my_ctrg, CTR_FLOOR),
+		.round_threshold_usec = UINT64_MAX, /* always >= gran_usec */
+		.T_gran = T_GRAN,
+		.T_forget_sum = T_FORGET_SUM,
+		.T_defs = g_my_obj_tdefs,
+	};
+}
+
+void my_obj_event(struct my_obj *my_obj, bool flag)
+{
+	osmo_time_cc_set_flag(&my_obj->flag_cc_ceil, flag);
+	osmo_time_cc_set_flag(&my_obj->flag_cc_round, flag);
+	osmo_time_cc_set_flag(&my_obj->flag_cc_floor, flag);
+}
+
+void my_obj_destruct(struct my_obj *my_obj)
+{
+	osmo_time_cc_cleanup(&my_obj->flag_cc_ceil);
+	osmo_time_cc_cleanup(&my_obj->flag_cc_round);
+	osmo_time_cc_cleanup(&my_obj->flag_cc_floor);
+}
+
+static const struct log_info_cat log_categories[] = {
+};
+
+static const struct log_info log_info = {
+	.cat = log_categories,
+	.num_cat = ARRAY_SIZE(log_categories),
+};
+
+int main()
+{
+	void *ctx = talloc_named_const(NULL, 0, "time_cc_test");
+	struct timespec *now;
+	struct my_obj my_obj = {0};
+
+	osmo_init_logging2(ctx, &log_info);
+
+	/* enable override for CLOCK_MONOTONIC */
+	osmo_clock_override_enable(CLOCK_MONOTONIC, true);
+	now = osmo_clock_override_gettimespec(CLOCK_MONOTONIC);
+	now->tv_sec = 23000;
+	now->tv_nsec = 0;
+
+	/* enable override for osmo_gettimeofday(), for osmo_timer_schedule() */
+	osmo_gettimeofday_override = true;
+	osmo_gettimeofday_override_time = (struct timeval){23000, 0};
+
+	my_ctrg = rate_ctr_group_alloc(ctx, &my_ctrg_desc, 0);
+
+#define CHECK_RATE_CTRS(exp_ceil, exp_round, exp_floor) do { \
+		printf("%d CHECK_RATE_CTRS(" #exp_ceil ", " #exp_round ", " #exp_floor ")", \
+		       my_obj.flag_cc_round.flag_state); \
+		while (osmo_select_main_ctx(1) > 0); \
+		if (exp_ceil != my_obj.flag_cc_ceil.cfg.rate_ctr->current \
+		    || exp_round != my_obj.flag_cc_round.cfg.rate_ctr->current \
+		    || exp_floor != my_obj.flag_cc_floor.cfg.rate_ctr->current) \
+			printf("\n     ERROR on line %d: ctr_ceil=%"PRIu64" ctr_round=%"PRIu64" ctr_floor=%"PRIu64"\n", \
+			       __LINE__, \
+			       my_obj.flag_cc_ceil.cfg.rate_ctr->current, \
+			       my_obj.flag_cc_round.cfg.rate_ctr->current, \
+			       my_obj.flag_cc_floor.cfg.rate_ctr->current); \
+		else \
+			printf(" ok\n"); \
+	} while (0)
+
+#define ADD_MILLISECS_NO_SELECT(ms) do { \
+		osmo_clock_override_add(CLOCK_MONOTONIC, ms / 1000, (uint64_t)(ms % 1000) * 1000000); \
+		osmo_gettimeofday_override_add(ms / 1000, (uint64_t)(ms % 1000) * 1000); \
+		printf("%d ADD_MILLISECS(" #ms ") --> %ld.%03ld", my_obj.flag_cc_round.flag_state, \
+		       now->tv_sec, now->tv_nsec/1000000); \
+		printf("\n"); \
+	} while (0)
+
+#define ADD_MILLISECS(ms) do { \
+		ADD_MILLISECS_NO_SELECT(ms); \
+		while (osmo_select_main_ctx(1) > 0); \
+	} while (0)
+
+#define FLAG(VAL) do { \
+		printf("  flag: %s -> %s\n", my_obj.flag_cc_round.flag_state ? "TRUE" : "FALSE", VAL ? "TRUE" : "FALSE"); \
+		my_obj_event(&my_obj, VAL); \
+	} while (0)
+
+	/*
+	 *                        sum ^
+	 *                            |                                          ________
+	 *                            |                                         /
+	 *                            |                                        /
+	 *                            |                                       /
+	 *                   3*gran --+--------------------------------------+
+	 *                            |                                     /:
+	 *                            |                                    / :
+	 *                            | - - - - - - - - - - - - - - - - - /  :
+	 *                            |                                  /.  :
+	 *                            |                                 / .  :
+	 *                   2*gran --+--------------------------------+  .  :
+	 *                            |                               /:  .  :
+	 *                            |                              / :  .  :
+	 *                            | - - - - - - - - - -_________/  :  .  :
+	 *                            |                   /         .  :  .  :
+	 *                            |                  /          .  :  .  :
+	 *                   1*gran --+-----------------+           .  :  .  :
+	 *                            |                /:           .  :  .  :
+	 *                            |               / :           .  :  .  :
+	 *                            | - - - - - - -/  :           .  :  .  :
+	 *                            |             /.  :           .  :  .  :
+	 *                            | ....-------' .  :           .  :  .  :
+	 *                         0  +----------------------------------------------------------> elapsed time
+	 *                                           .  :           .  :  .  :
+	 *                               _   _      _______         ____________
+	 *                   flag:    __| |_| |____| .  :  |_______|.  :  .  :  |__________
+	 *                            f t f t f    t .  :  f       t.  :  .  :  f
+	 *   round_threshold_usec       :            .  :           .  :  .  :
+	 *                 = 1 usec:  0  1           .  :2          .  :3 .  :4  = "ceil()"
+	 *       = 0 == gran_usec/2:  0              1  :           2  :  3  :   = "round()"
+	 *              = gran_usec:  0                 1              2     3   = "floor()"
+	 */
+
+	printf("\n----------- cumulating time, without forget_sum\n\n");
+
+	my_obj_init(&my_obj);
+	CHECK_RATE_CTRS(0, 0, 0);
+
+	ADD_MILLISECS(100);
+	CHECK_RATE_CTRS(0, 0, 0);
+
+	FLAG(true);
+	/* flag has just turned true the first time */
+	CHECK_RATE_CTRS(0, 0, 0);
+	ADD_MILLISECS(1);
+	/* flag has been true for 0.001s */
+	CHECK_RATE_CTRS(1, 0, 0);
+	ADD_MILLISECS(99);
+	/* flag has been true for 0.1s */
+	CHECK_RATE_CTRS(1, 0, 0);
+	FLAG(false);
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	ADD_MILLISECS(100);
+
+	CHECK_RATE_CTRS(1, 0, 0);
+	FLAG(true);
+	CHECK_RATE_CTRS(1, 0, 0);
+	ADD_MILLISECS(100);
+	/* flag has been true for 0.2s */
+	CHECK_RATE_CTRS(1, 0, 0);
+	FLAG(false);
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	ADD_MILLISECS(300);
+
+	CHECK_RATE_CTRS(1, 0, 0);
+	FLAG(true);
+	CHECK_RATE_CTRS(1, 0, 0);
+	ADD_MILLISECS(299);
+	/* flag has been true for 0.499s */
+	CHECK_RATE_CTRS(1, 0, 0);
+	ADD_MILLISECS(1);
+	/* flag has been true for 0.5s */
+	CHECK_RATE_CTRS(1, 1, 0);
+	ADD_MILLISECS(499);
+	/* flag has been true for 0.999s */
+	CHECK_RATE_CTRS(1, 1, 0);
+	ADD_MILLISECS(1);
+	/* flag has been true for 1.0s */
+	CHECK_RATE_CTRS(1, 1, 1);
+	ADD_MILLISECS(1);
+	/* flag has been true for 1.001s */
+	CHECK_RATE_CTRS(2, 1, 1);
+	ADD_MILLISECS(299);
+	/* flag has been true for 1.3s */
+	CHECK_RATE_CTRS(2, 1, 1);
+	FLAG(false);
+	CHECK_RATE_CTRS(2, 1, 1);
+
+	ADD_MILLISECS(400);
+
+	CHECK_RATE_CTRS(2, 1, 1);
+	FLAG(true);
+	CHECK_RATE_CTRS(2, 1, 1);
+	ADD_MILLISECS(199);
+	/* flag has been true for 1.499s */
+	CHECK_RATE_CTRS(2, 1, 1);
+	ADD_MILLISECS(2);
+	/* flag has been true for 1.501s */
+	CHECK_RATE_CTRS(2, 2, 1);
+	ADD_MILLISECS(498);
+	/* flag has been true for 1.999s */
+	CHECK_RATE_CTRS(2, 2, 1);
+	ADD_MILLISECS(2);
+	/* flag has been true for 2.001s */
+	CHECK_RATE_CTRS(3, 2, 2);
+	ADD_MILLISECS(500);
+	/* flag has been true for 2.501s */
+	CHECK_RATE_CTRS(3, 3, 2);
+	ADD_MILLISECS(498);
+	/* flag has been true for 2.999s */
+	CHECK_RATE_CTRS(3, 3, 2);
+	ADD_MILLISECS(3);
+	/* flag has been true for 3.003s */
+	CHECK_RATE_CTRS(4, 3, 3);
+	ADD_MILLISECS(200);
+	/* flag has been true for 3.203s */
+	CHECK_RATE_CTRS(4, 3, 3);
+	FLAG(false);
+	CHECK_RATE_CTRS(4, 3, 3);
+
+	ADD_MILLISECS(4321);
+	CHECK_RATE_CTRS(4, 3, 3);
+
+	FLAG(true);
+	CHECK_RATE_CTRS(4, 3, 3);
+	ADD_MILLISECS(5678);
+	CHECK_RATE_CTRS(9, 9, 8);
+	FLAG(false);
+	CHECK_RATE_CTRS(9, 9, 8);
+
+	my_obj_destruct(&my_obj);
+	rate_ctr_group_reset(my_ctrg);
+
+	printf("\n----------- test forget_sum_usec\n\n");
+	osmo_tdef_set(g_my_obj_tdefs, T_FORGET_SUM, 10, OSMO_TDEF_S);
+
+	now->tv_sec = 23000;
+	now->tv_nsec = 0;
+	osmo_gettimeofday_override_time = (struct timeval){23000, 0};
+
+	my_obj_init(&my_obj);
+
+	CHECK_RATE_CTRS(0, 0, 0);
+
+	FLAG(true);
+	/* flag has just turned true the first time */
+	CHECK_RATE_CTRS(0, 0, 0);
+	ADD_MILLISECS(100);
+	/* flag has been true for 0.1s */
+	CHECK_RATE_CTRS(1, 0, 0);
+	FLAG(false);
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	ADD_MILLISECS(1000);
+	/* 1 s of being false, forget_sum_usec has not yet occurred */
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	ADD_MILLISECS(8999);
+	/* 9.999 s of being false, forget_sum_usec has not yet occurred */
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	ADD_MILLISECS(1);
+	/* 10 s of being false, forget_sum_usec has occurred */
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	FLAG(true);
+	CHECK_RATE_CTRS(1, 0, 0);
+	ADD_MILLISECS(1);
+	/* Since previous sums were forgotton, ceil() triggers again */
+	CHECK_RATE_CTRS(2, 0, 0);
+	/* If the sum had not been forgotten, adding 400 ms to the initial 100 ms would have triggered round(). Verify
+	 * that this does not occur, since now full 500 ms are required */
+	ADD_MILLISECS(399);
+	CHECK_RATE_CTRS(2, 0, 0);
+	/* Adding another 100 ms will trigger round() */
+	ADD_MILLISECS(99);
+	CHECK_RATE_CTRS(2, 0, 0);
+	ADD_MILLISECS(1);
+	CHECK_RATE_CTRS(2, 1, 0);
+	/* If the sum had not been forgotten, adding 900 ms to the initial 100 ms would have triggered floor(). Verify
+	 * that this does not occur, since now full 1000 ms are required. We already added 500 ms above. */
+	ADD_MILLISECS(400);
+	CHECK_RATE_CTRS(2, 1, 0);
+	/* Adding another 100 ms will trigger floor() */
+	ADD_MILLISECS(99);
+	CHECK_RATE_CTRS(2, 1, 0);
+	ADD_MILLISECS(1);
+	CHECK_RATE_CTRS(2, 1, 1);
+
+	/* Test that durations of false below forget_sum_usec never trigger a forget */
+	ADD_MILLISECS(300);
+	CHECK_RATE_CTRS(3, 1, 1);
+	/* internal counter is now at 0.3s above the last reported rate counter */
+	FLAG(false);
+	ADD_MILLISECS(9999);
+	FLAG(true);
+	ADD_MILLISECS(25);
+	FLAG(false);
+	ADD_MILLISECS(9999);
+	FLAG(true);
+	ADD_MILLISECS(25);
+	FLAG(false);
+	ADD_MILLISECS(9999);
+	FLAG(true);
+	ADD_MILLISECS(25);
+	FLAG(false);
+	ADD_MILLISECS(9999);
+	FLAG(true);
+	ADD_MILLISECS(25);
+	/* internal counter is now at 0.4s above the last reported rate counter */
+	CHECK_RATE_CTRS(3, 1, 1);
+	ADD_MILLISECS(100);
+	CHECK_RATE_CTRS(3, 2, 1);
+	ADD_MILLISECS(500);
+	CHECK_RATE_CTRS(3, 2, 2);
+
+	/* Test that repeated osmo_time_cc_set_flag(false) does not cancel a forget_sum_usec */
+	ADD_MILLISECS(300);
+	/* internal counter is now at 0.3s above the last reported rate counter */
+	CHECK_RATE_CTRS(4, 2, 2);
+	FLAG(false);
+	ADD_MILLISECS(5000);
+	/* Repeat 'false', must not affect forget_sum_usec */
+	FLAG(false);
+	ADD_MILLISECS(5000);
+	CHECK_RATE_CTRS(4, 2, 2);
+	/* 10 s have passed, forget_sum_usec has occurred.
+	 * Hence ceil() will trigger again right away: */
+	FLAG(true);
+	ADD_MILLISECS(1);
+	CHECK_RATE_CTRS(5, 2, 2);
+	/* Adding 200 ms to the initial 300 ms would have triggered round(), but no more after forget_sum_usec */
+	ADD_MILLISECS(199);
+	CHECK_RATE_CTRS(5, 2, 2);
+	/* Adding another 300 ms will trigger round() */
+	ADD_MILLISECS(299);
+	CHECK_RATE_CTRS(5, 2, 2);
+	ADD_MILLISECS(1);
+	CHECK_RATE_CTRS(5, 3, 2);
+	/* Adding 700 ms to the initial 300 ms would have triggered ceil(), but no more after forget_sum_usec */
+	ADD_MILLISECS(200);
+	CHECK_RATE_CTRS(5, 3, 2);
+	/* Adding another 300 ms will trigger ceil() */
+	ADD_MILLISECS(299);
+	CHECK_RATE_CTRS(5, 3, 2);
+	ADD_MILLISECS(1);
+	CHECK_RATE_CTRS(5, 3, 3);
+
+	my_obj_destruct(&my_obj);
+	rate_ctr_group_reset(my_ctrg);
+
+
+	/* Verify correctness when select() lags and runs timer callbacks too late */
+	printf("\n----------- cumulating time, without forget_sum, when timer cb are invoked late\n\n");
+	osmo_tdef_set(g_my_obj_tdefs, T_FORGET_SUM, 0, OSMO_TDEF_S);
+	now->tv_sec = 23000;
+	now->tv_nsec = 0;
+	osmo_gettimeofday_override_time = (struct timeval){23000, 0};
+
+	my_obj_init(&my_obj);
+	CHECK_RATE_CTRS(0, 0, 0);
+
+	ADD_MILLISECS_NO_SELECT(100);
+	CHECK_RATE_CTRS(0, 0, 0);
+
+	FLAG(true);
+	/* flag has just turned true the first time */
+	CHECK_RATE_CTRS(0, 0, 0);
+	ADD_MILLISECS_NO_SELECT(100);
+	/* flag has been true for 0.1s */
+	CHECK_RATE_CTRS(1, 0, 0);
+	FLAG(false);
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	ADD_MILLISECS_NO_SELECT(100);
+
+	CHECK_RATE_CTRS(1, 0, 0);
+	FLAG(true);
+	CHECK_RATE_CTRS(1, 0, 0);
+	ADD_MILLISECS_NO_SELECT(100);
+	/* flag has been true for 0.2s */
+	CHECK_RATE_CTRS(1, 0, 0);
+	FLAG(false);
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	ADD_MILLISECS_NO_SELECT(300);
+
+	CHECK_RATE_CTRS(1, 0, 0);
+	FLAG(true);
+	CHECK_RATE_CTRS(1, 0, 0);
+	ADD_MILLISECS_NO_SELECT(799);
+	/* flag has been true for 0.999s */
+	CHECK_RATE_CTRS(1, 1, 0);
+	ADD_MILLISECS_NO_SELECT(1);
+	/* flag has been true for 1.0s */
+	CHECK_RATE_CTRS(1, 1, 1);
+	ADD_MILLISECS_NO_SELECT(300);
+	/* flag has been true for 1.3s */
+	CHECK_RATE_CTRS(2, 1, 1);
+	FLAG(false);
+	CHECK_RATE_CTRS(2, 1, 1);
+
+	ADD_MILLISECS_NO_SELECT(400);
+
+	CHECK_RATE_CTRS(2, 1, 1);
+	FLAG(true);
+	CHECK_RATE_CTRS(2, 1, 1);
+	ADD_MILLISECS_NO_SELECT(699);
+	/* flag has been true for 1.999s */
+	CHECK_RATE_CTRS(2, 2, 1);
+	ADD_MILLISECS_NO_SELECT(1);
+	/* flag has been true for 2.0s */
+	CHECK_RATE_CTRS(2, 2, 2);
+	ADD_MILLISECS_NO_SELECT(1);
+	/* flag has been true for 2.001s */
+	CHECK_RATE_CTRS(3, 2, 2);
+	ADD_MILLISECS_NO_SELECT(499);
+	/* flag has been true for 2.5s */
+	CHECK_RATE_CTRS(3, 3, 2);
+	ADD_MILLISECS_NO_SELECT(499);
+	/* flag has been true for 2.999s */
+	CHECK_RATE_CTRS(3, 3, 2);
+	ADD_MILLISECS_NO_SELECT(1);
+	/* flag has been true for 3.0s */
+	CHECK_RATE_CTRS(3, 3, 3);
+	ADD_MILLISECS_NO_SELECT(200);
+	/* flag has been true for 3.2s */
+	CHECK_RATE_CTRS(4, 3, 3);
+	FLAG(false);
+	CHECK_RATE_CTRS(4, 3, 3);
+
+	ADD_MILLISECS_NO_SELECT(4321);
+	CHECK_RATE_CTRS(4, 3, 3);
+
+	FLAG(true);
+	CHECK_RATE_CTRS(4, 3, 3);
+	ADD_MILLISECS_NO_SELECT(5678);
+	CHECK_RATE_CTRS(9, 9, 8);
+	FLAG(false);
+	CHECK_RATE_CTRS(9, 9, 8);
+
+	my_obj_destruct(&my_obj);
+	rate_ctr_group_reset(my_ctrg);
+
+
+	printf("\n----------- test forget_sum, when timer cb are invoked late\n\n");
+	osmo_tdef_set(g_my_obj_tdefs, T_FORGET_SUM, 10, OSMO_TDEF_S);
+
+	now->tv_sec = 23000;
+	now->tv_nsec = 0;
+	osmo_gettimeofday_override_time = (struct timeval){23000, 0};
+
+	my_obj_init(&my_obj);
+
+	CHECK_RATE_CTRS(0, 0, 0);
+
+	FLAG(true);
+	/* flag has just turned true the first time */
+	CHECK_RATE_CTRS(0, 0, 0);
+	ADD_MILLISECS_NO_SELECT(100);
+	/* flag has been true for 0.1s */
+	CHECK_RATE_CTRS(1, 0, 0);
+	FLAG(false);
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	ADD_MILLISECS_NO_SELECT(1000);
+	/* 1 s of being false, forget_sum_usec has not yet occurred */
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	ADD_MILLISECS_NO_SELECT(8999);
+	/* 9.999 s of being false, forget_sum_usec has not yet occurred */
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	ADD_MILLISECS_NO_SELECT(1);
+	/* 10 s of being false, forget_sum_usec has occurred */
+	CHECK_RATE_CTRS(1, 0, 0);
+
+	FLAG(true);
+	CHECK_RATE_CTRS(1, 0, 0);
+	ADD_MILLISECS_NO_SELECT(1);
+	/* Since previous sums were forgotton, ceil() triggers again */
+	CHECK_RATE_CTRS(2, 0, 0);
+	/* If the sum had not been forgotten, adding 400 ms to the initial 100 ms would have triggered round(). Verify
+	 * that this does not occur, since now full 500 ms are required */
+	ADD_MILLISECS_NO_SELECT(399);
+	CHECK_RATE_CTRS(2, 0, 0);
+	/* Adding another 100 ms will trigger round() */
+	ADD_MILLISECS_NO_SELECT(99);
+	CHECK_RATE_CTRS(2, 0, 0);
+	ADD_MILLISECS_NO_SELECT(1);
+	CHECK_RATE_CTRS(2, 1, 0);
+	/* If the sum had not been forgotten, adding 900 ms to the initial 100 ms would have triggered floor(). Verify
+	 * that this does not occur, since now full 1000 ms are required. We already added 500 ms above. */
+	ADD_MILLISECS_NO_SELECT(400);
+	CHECK_RATE_CTRS(2, 1, 0);
+	/* Adding another 100 ms will trigger floor() */
+	ADD_MILLISECS_NO_SELECT(99);
+	CHECK_RATE_CTRS(2, 1, 0);
+	ADD_MILLISECS_NO_SELECT(1);
+	CHECK_RATE_CTRS(2, 1, 1);
+
+	/* Test that durations of false below forget_sum_usec never trigger a forget */
+	ADD_MILLISECS_NO_SELECT(300);
+	CHECK_RATE_CTRS(3, 1, 1);
+	/* internal counter is now at 0.3s above the last reported rate counter */
+	FLAG(false);
+	ADD_MILLISECS_NO_SELECT(9999);
+	FLAG(true);
+	ADD_MILLISECS_NO_SELECT(25);
+	FLAG(false);
+	ADD_MILLISECS_NO_SELECT(9999);
+	FLAG(true);
+	ADD_MILLISECS_NO_SELECT(25);
+	FLAG(false);
+	ADD_MILLISECS_NO_SELECT(9999);
+	FLAG(true);
+	ADD_MILLISECS_NO_SELECT(25);
+	FLAG(false);
+	ADD_MILLISECS_NO_SELECT(9999);
+	FLAG(true);
+	ADD_MILLISECS_NO_SELECT(25);
+	/* internal counter is now at 0.4s above the last reported rate counter */
+	CHECK_RATE_CTRS(3, 1, 1);
+	ADD_MILLISECS_NO_SELECT(100);
+	CHECK_RATE_CTRS(3, 2, 1);
+	ADD_MILLISECS_NO_SELECT(500);
+	CHECK_RATE_CTRS(3, 2, 2);
+
+	my_obj_destruct(&my_obj);
+	rate_ctr_group_reset(my_ctrg);
+
+
+#define SET_TDEFS(gran, round_thresh, forget_sum) do { \
+		osmo_tdef_set(g_my_obj_tdefs, T_GRAN, gran, OSMO_TDEF_MS); \
+		osmo_tdef_set(g_my_obj_tdefs, T_ROUND_THRESH, round_thresh, OSMO_TDEF_MS); \
+		osmo_tdef_set(g_my_obj_tdefs, T_FORGET_SUM, forget_sum, OSMO_TDEF_S); \
+		printf("T_defs: T_gran=%luusec T_round_threshold=%luusec T_forget_sum=%luusec\n", \
+		       osmo_tdef_get(g_my_obj_tdefs, T_GRAN, OSMO_TDEF_US, -1), \
+		       osmo_tdef_get(g_my_obj_tdefs, T_ROUND_THRESH, OSMO_TDEF_US, -1), \
+		       osmo_tdef_get(g_my_obj_tdefs, T_FORGET_SUM, OSMO_TDEF_US, -1)); \
+	} while (0)
+
+	printf("\n----------- test T_defs\n\n");
+	now->tv_sec = 23000;
+	now->tv_nsec = 0;
+	osmo_gettimeofday_override_time = (struct timeval){23000, 0};
+
+	SET_TDEFS(100, 10, 0);
+
+	my_obj_init(&my_obj);
+	CHECK_RATE_CTRS(0, 0, 0);
+
+	ADD_MILLISECS(100);
+	CHECK_RATE_CTRS(0, 0, 0);
+
+	FLAG(true);
+	/* flag has just turned true the first time */
+	CHECK_RATE_CTRS(0, 0, 0);
+	ADD_MILLISECS(9);
+	/* flag has been true for 0.009s */
+	CHECK_RATE_CTRS(1, 0, 0);
+	ADD_MILLISECS(1);
+	/* flag has been true for 0.010s */
+	CHECK_RATE_CTRS(1, 1, 0);
+	ADD_MILLISECS(90);
+	/* flag has been true for 0.1s */
+	CHECK_RATE_CTRS(1, 1, 1);
+
+	SET_TDEFS(200, 190, 1);
+	/* gran is changed to 200ms, but still continues until the next scheduled event until the change is picked up.
+	 * For ceil(), it is 1 ms ahead.
+	 * For round(), it is 10 ms ahead.
+	 * For floor(), it is at the next full (previous) gran 100 ms ahead.
+	 * When T_defs change, all internal sums are reset to zero without reporting.
+	 */
+	CHECK_RATE_CTRS(1, 1, 1);
+	ADD_MILLISECS(1);
+	/* 1ms elapsed: ceil() picks up the T_gran change, starts anew. */
+	/* elapsed: ceil 0 ms */
+	CHECK_RATE_CTRS(1, 1, 1);
+	ADD_MILLISECS(1);
+	/* elapsed: ceil 1 ms */
+	/* ceil() increments because flag has been true for more than 1 us after reset */
+	CHECK_RATE_CTRS(2, 1, 1);
+	ADD_MILLISECS(8);
+	/* 10 ms elapsed: round() picks up the T_gran change, starts anew */
+	/* elapsed: ceil 9 ms, round 0 ms */
+	CHECK_RATE_CTRS(2, 1, 1);
+	ADD_MILLISECS(90);
+	/* 100 ms elapsed: floor() picks up the T_gran change, starts anew */
+	/* elapsed: ceil 99 ms, round 90 ms, floor 0 ms */
+	CHECK_RATE_CTRS(2, 1, 1);
+	ADD_MILLISECS(99);
+	/* elapsed: ceil 198 ms, round 189 ms, floor 99 ms */
+	CHECK_RATE_CTRS(2, 1, 1);
+	ADD_MILLISECS(1);
+	/* elapsed: ceil 199 ms, round 190 ms, floor 100 ms */
+	CHECK_RATE_CTRS(2, 2, 1);
+	ADD_MILLISECS(1);
+	/* elapsed: ceil 200 ms, round 191 ms, floor 101 ms */
+	CHECK_RATE_CTRS(2, 2, 1);
+	ADD_MILLISECS(1);
+	/* elapsed: ceil 201 ms, round 192 ms, floor 102 ms */
+	CHECK_RATE_CTRS(3, 2, 1);
+	ADD_MILLISECS(98);
+	/* elapsed: ceil 299 ms, round 290 ms, floor 200 ms */
+	CHECK_RATE_CTRS(3, 2, 2);
+	ADD_MILLISECS(99);
+	/* elapsed: ceil 398 ms, round 389 ms, floor 299 ms */
+	CHECK_RATE_CTRS(3, 2, 2);
+	ADD_MILLISECS(1);
+	/* elapsed: ceil 399 ms, round 390 ms, floor 300 ms */
+	CHECK_RATE_CTRS(3, 3, 2);
+	ADD_MILLISECS(1);
+	/* elapsed: ceil 400 ms, round 391 ms, floor 301 ms */
+	CHECK_RATE_CTRS(3, 3, 2);
+	ADD_MILLISECS(1);
+	/* elapsed: ceil 401 ms, round 392 ms, floor 302 ms */
+	CHECK_RATE_CTRS(4, 3, 2);
+	ADD_MILLISECS(98);
+	/* elapsed: ceil 499 ms, round 490 ms, floor 400 ms */
+	CHECK_RATE_CTRS(4, 3, 3);
+
+
+	SET_TDEFS(100, 0, 0);
+	/* T_defs change, but they only get picked up upon the next event:
+	 * For ceil(), it is 102 ms ahead.
+	 * For round(), it is 100 ms ahead (thresh is still 190, currently at 90).
+	 * For floor(), it is 200 ms ahead.
+	 * When T_defs change, all internal sums are reset to zero without reporting.
+	 */
+	CHECK_RATE_CTRS(4, 3, 3);
+	ADD_MILLISECS(100);
+	CHECK_RATE_CTRS(4, 3, 3);
+	/* round() picks up the new T_defs. Internal sum resets, nothing else happens yet.
+	 * round() schedules the next event 50 ms ahead. */
+	ADD_MILLISECS(2);
+	CHECK_RATE_CTRS(4, 3, 3);
+	/* ceil() picks up the change, its next event is 1 ms ahead. */
+	ADD_MILLISECS(1);
+	/* ceil: 0.001
+	 * round: 0.003
+	 * floor: still 97 ms until it picks up the change */
+	CHECK_RATE_CTRS(5, 3, 3);
+	ADD_MILLISECS(46);
+	CHECK_RATE_CTRS(5, 3, 3);
+	ADD_MILLISECS(1);
+	/* round() has first counter trigger after T_defs change. */
+	CHECK_RATE_CTRS(5, 4, 3);
+	/* ceil: 0.048
+	 * round: 0.050
+	 * floor: still 50 ms until it picks up the change */
+	ADD_MILLISECS(50);
+	/* floor() picks up the change. nothing happens yet. */
+	/* ceil: 0.098
+	 * round: 0.100
+	 * floor: 0.0 */
+	ADD_MILLISECS(2);
+	/* ceil: 0.100
+	 * round: 0.102
+	 * floor: 0.002 */
+	CHECK_RATE_CTRS(5, 4, 3);
+	ADD_MILLISECS(1);
+	/* ceil: 0.101
+	 * round: 0.103
+	 * floor: 0.003 */
+	CHECK_RATE_CTRS(6, 4, 3);
+	ADD_MILLISECS(46);
+	/* ceil: 0.147
+	 * round: 0.149
+	 * floor: 0.049 */
+	CHECK_RATE_CTRS(6, 4, 3);
+	ADD_MILLISECS(1);
+	/* ceil: 0.148
+	 * round: 0.150
+	 * floor: 0.050 */
+	CHECK_RATE_CTRS(6, 5, 3);
+
+	my_obj_destruct(&my_obj);
+	rate_ctr_group_reset(my_ctrg);
+
+	return 0;
+}
diff --git a/tests/time_cc/time_cc_test.ok b/tests/time_cc/time_cc_test.ok
new file mode 100644
index 0000000..ccf84d9
--- /dev/null
+++ b/tests/time_cc/time_cc_test.ok
@@ -0,0 +1,328 @@
+
+----------- cumulating time, without forget_sum
+
+0 CHECK_RATE_CTRS(0, 0, 0) ok
+0 ADD_MILLISECS(100) --> 23000.100
+0 CHECK_RATE_CTRS(0, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(0, 0, 0) ok
+1 ADD_MILLISECS(1) --> 23000.101
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+1 ADD_MILLISECS(99) --> 23000.200
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+0 ADD_MILLISECS(100) --> 23000.300
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+1 ADD_MILLISECS(100) --> 23000.400
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+0 ADD_MILLISECS(300) --> 23000.700
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+1 ADD_MILLISECS(299) --> 23000.999
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+1 ADD_MILLISECS(1) --> 23001.000
+1 CHECK_RATE_CTRS(1, 1, 0) ok
+1 ADD_MILLISECS(499) --> 23001.499
+1 CHECK_RATE_CTRS(1, 1, 0) ok
+1 ADD_MILLISECS(1) --> 23001.500
+1 CHECK_RATE_CTRS(1, 1, 1) ok
+1 ADD_MILLISECS(1) --> 23001.501
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+1 ADD_MILLISECS(299) --> 23001.800
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(2, 1, 1) ok
+0 ADD_MILLISECS(400) --> 23002.200
+0 CHECK_RATE_CTRS(2, 1, 1) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+1 ADD_MILLISECS(199) --> 23002.399
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+1 ADD_MILLISECS(2) --> 23002.401
+1 CHECK_RATE_CTRS(2, 2, 1) ok
+1 ADD_MILLISECS(498) --> 23002.899
+1 CHECK_RATE_CTRS(2, 2, 1) ok
+1 ADD_MILLISECS(2) --> 23002.901
+1 CHECK_RATE_CTRS(3, 2, 2) ok
+1 ADD_MILLISECS(500) --> 23003.401
+1 CHECK_RATE_CTRS(3, 3, 2) ok
+1 ADD_MILLISECS(498) --> 23003.899
+1 CHECK_RATE_CTRS(3, 3, 2) ok
+1 ADD_MILLISECS(3) --> 23003.902
+1 CHECK_RATE_CTRS(4, 3, 3) ok
+1 ADD_MILLISECS(200) --> 23004.102
+1 CHECK_RATE_CTRS(4, 3, 3) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(4, 3, 3) ok
+0 ADD_MILLISECS(4321) --> 23008.423
+0 CHECK_RATE_CTRS(4, 3, 3) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(4, 3, 3) ok
+1 ADD_MILLISECS(5678) --> 23014.101
+1 CHECK_RATE_CTRS(9, 9, 8) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(9, 9, 8) ok
+
+----------- test forget_sum_usec
+
+0 CHECK_RATE_CTRS(0, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(0, 0, 0) ok
+1 ADD_MILLISECS(100) --> 23000.100
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+0 ADD_MILLISECS(1000) --> 23001.100
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+0 ADD_MILLISECS(8999) --> 23010.099
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+0 ADD_MILLISECS(1) --> 23010.100
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+1 ADD_MILLISECS(1) --> 23010.101
+1 CHECK_RATE_CTRS(2, 0, 0) ok
+1 ADD_MILLISECS(399) --> 23010.500
+1 CHECK_RATE_CTRS(2, 0, 0) ok
+1 ADD_MILLISECS(99) --> 23010.599
+1 CHECK_RATE_CTRS(2, 0, 0) ok
+1 ADD_MILLISECS(1) --> 23010.600
+1 CHECK_RATE_CTRS(2, 1, 0) ok
+1 ADD_MILLISECS(400) --> 23011.000
+1 CHECK_RATE_CTRS(2, 1, 0) ok
+1 ADD_MILLISECS(99) --> 23011.099
+1 CHECK_RATE_CTRS(2, 1, 0) ok
+1 ADD_MILLISECS(1) --> 23011.100
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+1 ADD_MILLISECS(300) --> 23011.400
+1 CHECK_RATE_CTRS(3, 1, 1) ok
+  flag: TRUE -> FALSE
+0 ADD_MILLISECS(9999) --> 23021.399
+  flag: FALSE -> TRUE
+1 ADD_MILLISECS(25) --> 23021.424
+  flag: TRUE -> FALSE
+0 ADD_MILLISECS(9999) --> 23031.423
+  flag: FALSE -> TRUE
+1 ADD_MILLISECS(25) --> 23031.448
+  flag: TRUE -> FALSE
+0 ADD_MILLISECS(9999) --> 23041.447
+  flag: FALSE -> TRUE
+1 ADD_MILLISECS(25) --> 23041.472
+  flag: TRUE -> FALSE
+0 ADD_MILLISECS(9999) --> 23051.471
+  flag: FALSE -> TRUE
+1 ADD_MILLISECS(25) --> 23051.496
+1 CHECK_RATE_CTRS(3, 1, 1) ok
+1 ADD_MILLISECS(100) --> 23051.596
+1 CHECK_RATE_CTRS(3, 2, 1) ok
+1 ADD_MILLISECS(500) --> 23052.096
+1 CHECK_RATE_CTRS(3, 2, 2) ok
+1 ADD_MILLISECS(300) --> 23052.396
+1 CHECK_RATE_CTRS(4, 2, 2) ok
+  flag: TRUE -> FALSE
+0 ADD_MILLISECS(5000) --> 23057.396
+  flag: FALSE -> FALSE
+0 ADD_MILLISECS(5000) --> 23062.396
+0 CHECK_RATE_CTRS(4, 2, 2) ok
+  flag: FALSE -> TRUE
+1 ADD_MILLISECS(1) --> 23062.397
+1 CHECK_RATE_CTRS(5, 2, 2) ok
+1 ADD_MILLISECS(199) --> 23062.596
+1 CHECK_RATE_CTRS(5, 2, 2) ok
+1 ADD_MILLISECS(299) --> 23062.895
+1 CHECK_RATE_CTRS(5, 2, 2) ok
+1 ADD_MILLISECS(1) --> 23062.896
+1 CHECK_RATE_CTRS(5, 3, 2) ok
+1 ADD_MILLISECS(200) --> 23063.096
+1 CHECK_RATE_CTRS(5, 3, 2) ok
+1 ADD_MILLISECS(299) --> 23063.395
+1 CHECK_RATE_CTRS(5, 3, 2) ok
+1 ADD_MILLISECS(1) --> 23063.396
+1 CHECK_RATE_CTRS(5, 3, 3) ok
+
+----------- cumulating time, without forget_sum, when timer cb are invoked late
+
+0 CHECK_RATE_CTRS(0, 0, 0) ok
+0 ADD_MILLISECS(100) --> 23000.100
+0 CHECK_RATE_CTRS(0, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(0, 0, 0) ok
+1 ADD_MILLISECS(100) --> 23000.200
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+0 ADD_MILLISECS(100) --> 23000.300
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+1 ADD_MILLISECS(100) --> 23000.400
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+0 ADD_MILLISECS(300) --> 23000.700
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+1 ADD_MILLISECS(799) --> 23001.499
+1 CHECK_RATE_CTRS(1, 1, 0) ok
+1 ADD_MILLISECS(1) --> 23001.500
+1 CHECK_RATE_CTRS(1, 1, 1) ok
+1 ADD_MILLISECS(300) --> 23001.800
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(2, 1, 1) ok
+0 ADD_MILLISECS(400) --> 23002.200
+0 CHECK_RATE_CTRS(2, 1, 1) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+1 ADD_MILLISECS(699) --> 23002.899
+1 CHECK_RATE_CTRS(2, 2, 1) ok
+1 ADD_MILLISECS(1) --> 23002.900
+1 CHECK_RATE_CTRS(2, 2, 2) ok
+1 ADD_MILLISECS(1) --> 23002.901
+1 CHECK_RATE_CTRS(3, 2, 2) ok
+1 ADD_MILLISECS(499) --> 23003.400
+1 CHECK_RATE_CTRS(3, 3, 2) ok
+1 ADD_MILLISECS(499) --> 23003.899
+1 CHECK_RATE_CTRS(3, 3, 2) ok
+1 ADD_MILLISECS(1) --> 23003.900
+1 CHECK_RATE_CTRS(3, 3, 3) ok
+1 ADD_MILLISECS(200) --> 23004.100
+1 CHECK_RATE_CTRS(4, 3, 3) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(4, 3, 3) ok
+0 ADD_MILLISECS(4321) --> 23008.421
+0 CHECK_RATE_CTRS(4, 3, 3) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(4, 3, 3) ok
+1 ADD_MILLISECS(5678) --> 23014.099
+1 CHECK_RATE_CTRS(9, 9, 8) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(9, 9, 8) ok
+
+----------- test forget_sum, when timer cb are invoked late
+
+0 CHECK_RATE_CTRS(0, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(0, 0, 0) ok
+1 ADD_MILLISECS(100) --> 23000.100
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: TRUE -> FALSE
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+0 ADD_MILLISECS(1000) --> 23001.100
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+0 ADD_MILLISECS(8999) --> 23010.099
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+0 ADD_MILLISECS(1) --> 23010.100
+0 CHECK_RATE_CTRS(1, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+1 ADD_MILLISECS(1) --> 23010.101
+1 CHECK_RATE_CTRS(2, 0, 0) ok
+1 ADD_MILLISECS(399) --> 23010.500
+1 CHECK_RATE_CTRS(2, 0, 0) ok
+1 ADD_MILLISECS(99) --> 23010.599
+1 CHECK_RATE_CTRS(2, 0, 0) ok
+1 ADD_MILLISECS(1) --> 23010.600
+1 CHECK_RATE_CTRS(2, 1, 0) ok
+1 ADD_MILLISECS(400) --> 23011.000
+1 CHECK_RATE_CTRS(2, 1, 0) ok
+1 ADD_MILLISECS(99) --> 23011.099
+1 CHECK_RATE_CTRS(2, 1, 0) ok
+1 ADD_MILLISECS(1) --> 23011.100
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+1 ADD_MILLISECS(300) --> 23011.400
+1 CHECK_RATE_CTRS(3, 1, 1) ok
+  flag: TRUE -> FALSE
+0 ADD_MILLISECS(9999) --> 23021.399
+  flag: FALSE -> TRUE
+1 ADD_MILLISECS(25) --> 23021.424
+  flag: TRUE -> FALSE
+0 ADD_MILLISECS(9999) --> 23031.423
+  flag: FALSE -> TRUE
+1 ADD_MILLISECS(25) --> 23031.448
+  flag: TRUE -> FALSE
+0 ADD_MILLISECS(9999) --> 23041.447
+  flag: FALSE -> TRUE
+1 ADD_MILLISECS(25) --> 23041.472
+  flag: TRUE -> FALSE
+0 ADD_MILLISECS(9999) --> 23051.471
+  flag: FALSE -> TRUE
+1 ADD_MILLISECS(25) --> 23051.496
+1 CHECK_RATE_CTRS(3, 1, 1) ok
+1 ADD_MILLISECS(100) --> 23051.596
+1 CHECK_RATE_CTRS(3, 2, 1) ok
+1 ADD_MILLISECS(500) --> 23052.096
+1 CHECK_RATE_CTRS(3, 2, 2) ok
+
+----------- test T_defs
+
+T_defs: T_gran=100000usec T_round_threshold=10000usec T_forget_sum=0usec
+0 CHECK_RATE_CTRS(0, 0, 0) ok
+0 ADD_MILLISECS(100) --> 23000.100
+0 CHECK_RATE_CTRS(0, 0, 0) ok
+  flag: FALSE -> TRUE
+1 CHECK_RATE_CTRS(0, 0, 0) ok
+1 ADD_MILLISECS(9) --> 23000.109
+1 CHECK_RATE_CTRS(1, 0, 0) ok
+1 ADD_MILLISECS(1) --> 23000.110
+1 CHECK_RATE_CTRS(1, 1, 0) ok
+1 ADD_MILLISECS(90) --> 23000.200
+1 CHECK_RATE_CTRS(1, 1, 1) ok
+T_defs: T_gran=200000usec T_round_threshold=190000usec T_forget_sum=1000000usec
+1 CHECK_RATE_CTRS(1, 1, 1) ok
+1 ADD_MILLISECS(1) --> 23000.201
+1 CHECK_RATE_CTRS(1, 1, 1) ok
+1 ADD_MILLISECS(1) --> 23000.202
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+1 ADD_MILLISECS(8) --> 23000.210
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+1 ADD_MILLISECS(90) --> 23000.300
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+1 ADD_MILLISECS(99) --> 23000.399
+1 CHECK_RATE_CTRS(2, 1, 1) ok
+1 ADD_MILLISECS(1) --> 23000.400
+1 CHECK_RATE_CTRS(2, 2, 1) ok
+1 ADD_MILLISECS(1) --> 23000.401
+1 CHECK_RATE_CTRS(2, 2, 1) ok
+1 ADD_MILLISECS(1) --> 23000.402
+1 CHECK_RATE_CTRS(3, 2, 1) ok
+1 ADD_MILLISECS(98) --> 23000.500
+1 CHECK_RATE_CTRS(3, 2, 2) ok
+1 ADD_MILLISECS(99) --> 23000.599
+1 CHECK_RATE_CTRS(3, 2, 2) ok
+1 ADD_MILLISECS(1) --> 23000.600
+1 CHECK_RATE_CTRS(3, 3, 2) ok
+1 ADD_MILLISECS(1) --> 23000.601
+1 CHECK_RATE_CTRS(3, 3, 2) ok
+1 ADD_MILLISECS(1) --> 23000.602
+1 CHECK_RATE_CTRS(4, 3, 2) ok
+1 ADD_MILLISECS(98) --> 23000.700
+1 CHECK_RATE_CTRS(4, 3, 3) ok
+T_defs: T_gran=100000usec T_round_threshold=0usec T_forget_sum=0usec
+1 CHECK_RATE_CTRS(4, 3, 3) ok
+1 ADD_MILLISECS(100) --> 23000.800
+1 CHECK_RATE_CTRS(4, 3, 3) ok
+1 ADD_MILLISECS(2) --> 23000.802
+1 CHECK_RATE_CTRS(4, 3, 3) ok
+1 ADD_MILLISECS(1) --> 23000.803
+1 CHECK_RATE_CTRS(5, 3, 3) ok
+1 ADD_MILLISECS(46) --> 23000.849
+1 CHECK_RATE_CTRS(5, 3, 3) ok
+1 ADD_MILLISECS(1) --> 23000.850
+1 CHECK_RATE_CTRS(5, 4, 3) ok
+1 ADD_MILLISECS(50) --> 23000.900
+1 ADD_MILLISECS(2) --> 23000.902
+1 CHECK_RATE_CTRS(5, 4, 3) ok
+1 ADD_MILLISECS(1) --> 23000.903
+1 CHECK_RATE_CTRS(6, 4, 3) ok
+1 ADD_MILLISECS(46) --> 23000.949
+1 CHECK_RATE_CTRS(6, 4, 3) ok
+1 ADD_MILLISECS(1) --> 23000.950
+1 CHECK_RATE_CTRS(6, 5, 3) ok