diff --git a/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/CMakeLists.txt b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/CMakeLists.txt
new file mode 100644
index 0000000..5c7d106
--- /dev/null
+++ b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/CMakeLists.txt
@@ -0,0 +1,30 @@
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(lwm2m_rd_client)
+
+set(APP_SRC_DIR ${CMAKE_CURRENT_SOURCE_DIR}/src)
+
+# Add test sources
+target_sources(app PRIVATE ${APP_SRC_DIR}/main.c)
+target_sources(app PRIVATE ${APP_SRC_DIR}/stubs.c)
+target_sources(app PRIVATE ${ZEPHYR_BASE}/subsys/net/lib/lwm2m/lwm2m_rd_client.c)
+
+# Add includes directories
+target_include_directories(app PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/src)
+target_include_directories(app PRIVATE ${ZEPHYR_BASE}/include/)
+target_include_directories(app PRIVATE ${ZEPHYR_BASE}/subsys/net/lib/lwm2m/)
+
+add_compile_definitions(CONFIG_LWM2M_ENGINE_MAX_PENDING=2)
+add_compile_definitions(CONFIG_LWM2M_ENGINE_MAX_REPLIES=2)
+add_compile_definitions(CONFIG_LWM2M_ENGINE_VALIDATION_BUFFER_SIZE=512)
+add_compile_definitions(CONFIG_LWM2M_ENGINE_MESSAGE_HEADER_SIZE=512)
+add_compile_definitions(CONFIG_LWM2M_RD_CLIENT_ENDPOINT_NAME_MAX_LENGTH=32)
+add_compile_definitions(CONFIG_LWM2M_RD_CLIENT_MAX_RETRIES=2)
+add_compile_definitions(CONFIG_LWM2M_COAP_BLOCK_SIZE=256)
+add_compile_definitions(CONFIG_LWM2M_COAP_MAX_MSG_SIZE=512)
+add_compile_definitions(CONFIG_LWM2M_ENGINE_DEFAULT_LIFETIME=60)
+add_compile_definitions(CONFIG_LWM2M_SECURITY_INSTANCE_COUNT=1)
+add_compile_definitions(CONFIG_LWM2M_SECONDS_TO_UPDATE_EARLY=30)
+add_compile_definitions(CONFIG_LWM2M_QUEUE_MODE_UPTIME=30)
+add_compile_definitions(CONFIG_LWM2M_LOG_LEVEL=4)
diff --git a/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/prj.conf b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/prj.conf
new file mode 100644
index 0000000..fce1a579
--- /dev/null
+++ b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/prj.conf
@@ -0,0 +1,3 @@
+CONFIG_ZTEST=y
+CONFIG_ZTEST_NEW_API=y
+CONFIG_ZTEST_STACK_SIZE=4096
diff --git a/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/src/main.c b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/src/main.c
new file mode 100644
index 0000000..d5fe2ed
--- /dev/null
+++ b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/src/main.c
@@ -0,0 +1,361 @@
+/*
+ * Copyright (c) 2022 grandcentrix GmbH
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "stubs.h"
+
+#include <zephyr/fff.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/ztest.h>
+
+#include <lwm2m_rd_client.h>
+
+LOG_MODULE_REGISTER(lwm2m_rd_client_test);
+
+DEFINE_FFF_GLOBALS;
+
+/* Maximum number of iterations within the state machine of RD Client
+ * service that is waited for until a possible event occurs
+ */
+static const uint8_t RD_CLIENT_MAX_LOOKUP_ITERATIONS = 10;
+
+FAKE_VOID_FUNC(show_lwm2m_event, enum lwm2m_rd_client_event);
+FAKE_VOID_FUNC(show_lwm2m_observe, enum lwm2m_observe_event);
+
+bool check_lwm2m_rd_client_event(uint8_t expected_val, uint8_t arg_index)
+{
+	int max_service_iterations = RD_CLIENT_MAX_LOOKUP_ITERATIONS;
+
+	while (max_service_iterations > 0) {
+		if (show_lwm2m_event_fake.call_count > arg_index) {
+			return show_lwm2m_event_fake.arg0_history[arg_index] == expected_val;
+		}
+
+		wait_for_service(1);
+		max_service_iterations--;
+	}
+
+	return false;
+}
+
+bool check_lwm2m_observe_event(uint8_t expected_val, uint8_t arg_index)
+{
+	int max_service_iterations = RD_CLIENT_MAX_LOOKUP_ITERATIONS;
+
+	while (max_service_iterations > 0) {
+		if (show_lwm2m_observe_fake.call_count > arg_index) {
+			return show_lwm2m_observe_fake.arg0_history[arg_index] == expected_val;
+		}
+
+		wait_for_service(1);
+		max_service_iterations--;
+	}
+
+	return false;
+}
+
+static void lwm2m_event_cb(struct lwm2m_ctx *client, enum lwm2m_rd_client_event client_event)
+{
+	ARG_UNUSED(client);
+
+	switch (client_event) {
+	case LWM2M_RD_CLIENT_EVENT_ENGINE_SUSPENDED:
+		LOG_INF("**** LWM2M_RD_CLIENT_EVENT_ENGINE_SUSPENDED");
+		break;
+	case LWM2M_RD_CLIENT_EVENT_REGISTRATION_FAILURE:
+		LOG_INF("**** LWM2M_RD_CLIENT_EVENT_REGISTRATION_FAILURE");
+		break;
+	case LWM2M_RD_CLIENT_EVENT_REG_TIMEOUT:
+		LOG_INF("**** LWM2M_RD_CLIENT_EVENT_REG_TIMEOUT");
+		break;
+	case LWM2M_RD_CLIENT_EVENT_DISCONNECT:
+		LOG_INF("**** LWM2M_RD_CLIENT_EVENT_DISCONNECT");
+		break;
+	case LWM2M_RD_CLIENT_EVENT_REGISTRATION_COMPLETE:
+		LOG_INF("**** LWM2M_RD_CLIENT_EVENT_REGISTRATION_COMPLETE");
+		break;
+	case LWM2M_RD_CLIENT_EVENT_REG_UPDATE_COMPLETE:
+		LOG_INF("**** LWM2M_RD_CLIENT_EVENT_REG_UPDATE_COMPLETE");
+		break;
+	case LWM2M_RD_CLIENT_EVENT_NETWORK_ERROR:
+		LOG_INF("**** LWM2M_RD_CLIENT_EVENT_NETWORK_ERROR");
+		break;
+	default:
+		break;
+	}
+
+	show_lwm2m_event(client_event);
+}
+
+static void lwm2m_observe_cb(enum lwm2m_observe_event event, struct lwm2m_obj_path *path,
+			     void *user_data)
+{
+	switch (event) {
+	case LWM2M_OBSERVE_EVENT_OBSERVER_ADDED:
+		LOG_INF("**** LWM2M_OBSERVE_EVENT_OBSERVER_ADDED");
+		break;
+	case LWM2M_OBSERVE_EVENT_NOTIFY_TIMEOUT:
+		LOG_INF("**** LWM2M_OBSERVE_EVENT_NOTIFY_TIMEOUT");
+		break;
+	case LWM2M_OBSERVE_EVENT_OBSERVER_REMOVED:
+		LOG_INF("**** LWM2M_OBSERVE_EVENT_OBSERVER_REMOVED");
+		break;
+	case LWM2M_OBSERVE_EVENT_NOTIFY_ACK:
+		LOG_INF("**** LWM2M_OBSERVE_EVENT_NOTIFY_ACK");
+		break;
+	default:
+		break;
+	}
+
+	show_lwm2m_observe(event);
+}
+
+#define FFF_FAKES_LIST(FAKE)
+
+static void my_suite_before(void *data)
+{
+	/* Register resets */
+	DO_FOREACH_FAKE(RESET_FAKE);
+
+	/* reset common FFF internal structures */
+	FFF_RESET_HISTORY();
+
+	RESET_FAKE(show_lwm2m_event);
+	RESET_FAKE(show_lwm2m_observe);
+
+	test_lwm2m_engine_stop_service();
+}
+
+void message_reply_cb_default(struct lwm2m_message *msg)
+{
+	struct coap_packet response;
+	struct coap_reply reply;
+	struct sockaddr from;
+
+	memset(&response, 0, sizeof(struct coap_packet));
+	memset(&reply, 0, sizeof(struct coap_reply));
+	memset(&from, 0, sizeof(struct sockaddr));
+
+	msg->reply_cb(&response, &reply, &from);
+}
+
+void message_reply_timeout_cb_default(struct lwm2m_message *msg)
+{
+	msg->message_timeout_cb(msg);
+}
+
+ZTEST_SUITE(lwm2m_rd_client, NULL, NULL, my_suite_before, NULL, NULL);
+
+ZTEST(lwm2m_rd_client, test_start_registration_ok)
+{
+	struct lwm2m_ctx ctx;
+
+	(void)memset(&ctx, 0x0, sizeof(ctx));
+
+	test_prepare_pending_message_cb(&message_reply_cb_default);
+
+	lwm2m_engine_add_service_fake.custom_fake = lwm2m_engine_add_service_fake_default;
+	lwm2m_rd_client_init();
+	test_lwm2m_engine_start_service();
+	wait_for_service(1);
+
+	lwm2m_get_bool_fake.custom_fake = lwm2m_get_bool_fake_default;
+	lwm2m_sprint_ip_addr_fake.custom_fake = lwm2m_sprint_ip_addr_fake_default;
+	lwm2m_init_message_fake.custom_fake = lwm2m_init_message_fake_default;
+	coap_header_get_code_fake.custom_fake = coap_header_get_code_fake_created;
+	coap_find_options_fake.custom_fake = coap_find_options_do_registration_reply_cb_ok;
+	zassert_true(lwm2m_rd_client_start(&ctx, "Test", 0, lwm2m_event_cb, lwm2m_observe_cb) == 0,
+		     NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REGISTRATION_COMPLETE, 0),
+		     NULL);
+
+	coap_header_get_code_fake.custom_fake = coap_header_get_code_fake_deleted;
+	zassert_true(lwm2m_rd_client_stop(&ctx, lwm2m_event_cb, true) == 0, NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_DISCONNECT, 1), NULL);
+}
+
+ZTEST(lwm2m_rd_client, test_start_registration_timeout)
+{
+	struct lwm2m_ctx ctx;
+
+	(void)memset(&ctx, 0x0, sizeof(ctx));
+
+	test_prepare_pending_message_cb(&message_reply_timeout_cb_default);
+
+	lwm2m_engine_add_service_fake.custom_fake = lwm2m_engine_add_service_fake_default;
+	lwm2m_rd_client_init();
+	test_lwm2m_engine_start_service();
+	wait_for_service(1);
+
+	lwm2m_get_bool_fake.custom_fake = lwm2m_get_bool_fake_default;
+	lwm2m_sprint_ip_addr_fake.custom_fake = lwm2m_sprint_ip_addr_fake_default;
+	lwm2m_init_message_fake.custom_fake = lwm2m_init_message_fake_default;
+	zassert_true(lwm2m_rd_client_start(&ctx, "Test", 0, lwm2m_event_cb, lwm2m_observe_cb) == 0,
+		     NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_DISCONNECT, 0), NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REG_TIMEOUT, 1), NULL);
+}
+
+ZTEST(lwm2m_rd_client, test_start_registration_fail)
+{
+	struct lwm2m_ctx ctx;
+
+	(void)memset(&ctx, 0x0, sizeof(ctx));
+
+	test_prepare_pending_message_cb(&message_reply_cb_default);
+
+	lwm2m_engine_add_service_fake.custom_fake = lwm2m_engine_add_service_fake_default;
+	lwm2m_rd_client_init();
+	test_lwm2m_engine_start_service();
+	wait_for_service(1);
+
+	lwm2m_get_bool_fake.custom_fake = lwm2m_get_bool_fake_default;
+	lwm2m_sprint_ip_addr_fake.custom_fake = lwm2m_sprint_ip_addr_fake_default;
+	lwm2m_init_message_fake.custom_fake = lwm2m_init_message_fake_default;
+	zassert_true(lwm2m_rd_client_start(&ctx, "Test", 0, lwm2m_event_cb, lwm2m_observe_cb) == 0,
+		     NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REGISTRATION_FAILURE, 0),
+		     NULL);
+}
+
+ZTEST(lwm2m_rd_client, test_start_registration_update)
+{
+	struct lwm2m_ctx ctx;
+
+	(void)memset(&ctx, 0x0, sizeof(ctx));
+
+	test_prepare_pending_message_cb(&message_reply_cb_default);
+
+	lwm2m_engine_add_service_fake.custom_fake = lwm2m_engine_add_service_fake_default;
+	lwm2m_rd_client_init();
+	test_lwm2m_engine_start_service();
+	wait_for_service(1);
+
+	lwm2m_get_bool_fake.custom_fake = lwm2m_get_bool_fake_default;
+	lwm2m_sprint_ip_addr_fake.custom_fake = lwm2m_sprint_ip_addr_fake_default;
+	lwm2m_init_message_fake.custom_fake = lwm2m_init_message_fake_default;
+	coap_header_get_code_fake.custom_fake = coap_header_get_code_fake_created;
+	coap_find_options_fake.custom_fake = coap_find_options_do_registration_reply_cb_ok;
+	zassert_true(lwm2m_rd_client_start(&ctx, "Test", 0, lwm2m_event_cb, lwm2m_observe_cb) == 0,
+		     NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REGISTRATION_COMPLETE, 0),
+		     NULL);
+
+	lwm2m_rd_client_update();
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REG_UPDATE_COMPLETE, 1),
+		     NULL);
+}
+
+ZTEST(lwm2m_rd_client, test_start_registration_update_fail)
+{
+	struct lwm2m_ctx ctx;
+
+	(void)memset(&ctx, 0x0, sizeof(ctx));
+
+	test_prepare_pending_message_cb(&message_reply_cb_default);
+
+	lwm2m_engine_add_service_fake.custom_fake = lwm2m_engine_add_service_fake_default;
+	lwm2m_rd_client_init();
+	test_lwm2m_engine_start_service();
+	wait_for_service(1);
+
+	lwm2m_get_bool_fake.custom_fake = lwm2m_get_bool_fake_default;
+	lwm2m_sprint_ip_addr_fake.custom_fake = lwm2m_sprint_ip_addr_fake_default;
+	lwm2m_init_message_fake.custom_fake = lwm2m_init_message_fake_default;
+	coap_header_get_code_fake.custom_fake = coap_header_get_code_fake_created;
+	coap_find_options_fake.custom_fake = coap_find_options_do_registration_reply_cb_ok;
+	zassert_true(lwm2m_rd_client_start(&ctx, "Test", 0, lwm2m_event_cb, lwm2m_observe_cb) == 0,
+		     NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REGISTRATION_COMPLETE, 0),
+		     NULL);
+
+	RESET_FAKE(coap_header_get_code);
+
+	lwm2m_rd_client_update();
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REGISTRATION_FAILURE, 1),
+		     NULL);
+}
+
+ZTEST(lwm2m_rd_client, test_error_on_registration_update)
+{
+	struct lwm2m_ctx ctx;
+
+	(void)memset(&ctx, 0x0, sizeof(ctx));
+
+	test_prepare_pending_message_cb(&message_reply_cb_default);
+
+	lwm2m_engine_add_service_fake.custom_fake = lwm2m_engine_add_service_fake_default;
+	lwm2m_rd_client_init();
+	test_lwm2m_engine_start_service();
+	wait_for_service(1);
+
+	lwm2m_get_bool_fake.custom_fake = lwm2m_get_bool_fake_default;
+	lwm2m_sprint_ip_addr_fake.custom_fake = lwm2m_sprint_ip_addr_fake_default;
+	lwm2m_init_message_fake.custom_fake = lwm2m_init_message_fake_default;
+	coap_header_get_code_fake.custom_fake = coap_header_get_code_fake_created;
+	coap_find_options_fake.custom_fake = coap_find_options_do_registration_reply_cb_ok;
+	zassert_true(lwm2m_rd_client_start(&ctx, "Test", 0, lwm2m_event_cb, lwm2m_observe_cb) == 0,
+		     NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REGISTRATION_COMPLETE, 0),
+		     NULL);
+
+	coap_packet_append_option_fake.custom_fake = coap_packet_append_option_fake_err;
+	lwm2m_rd_client_update();
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REGISTRATION_COMPLETE, 1),
+		     NULL);
+}
+
+ZTEST(lwm2m_rd_client, test_network_error_on_registration)
+{
+	struct lwm2m_ctx ctx;
+
+	(void)memset(&ctx, 0x0, sizeof(ctx));
+
+	lwm2m_engine_add_service_fake.custom_fake = lwm2m_engine_add_service_fake_default;
+	lwm2m_rd_client_init();
+	test_lwm2m_engine_start_service();
+	wait_for_service(1);
+
+	lwm2m_get_bool_fake.custom_fake = lwm2m_get_bool_fake_default;
+	lwm2m_sprint_ip_addr_fake.custom_fake = lwm2m_sprint_ip_addr_fake_default;
+	lwm2m_init_message_fake.custom_fake = lwm2m_init_message_fake_default;
+	coap_header_get_code_fake.custom_fake = coap_header_get_code_fake_created;
+	coap_find_options_fake.custom_fake = coap_find_options_do_registration_reply_cb_ok;
+	coap_packet_append_option_fake.custom_fake = coap_packet_append_option_fake_err;
+	zassert_true(lwm2m_rd_client_start(&ctx, "Test", 0, lwm2m_event_cb, lwm2m_observe_cb) == 0,
+		     NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_NETWORK_ERROR, 0), NULL);
+}
+
+ZTEST(lwm2m_rd_client, test_suspend_resume_registration)
+{
+	struct lwm2m_ctx ctx;
+
+	(void)memset(&ctx, 0x0, sizeof(ctx));
+
+	test_prepare_pending_message_cb(&message_reply_cb_default);
+
+	lwm2m_engine_add_service_fake.custom_fake = lwm2m_engine_add_service_fake_default;
+	lwm2m_rd_client_init();
+	test_lwm2m_engine_start_service();
+	wait_for_service(1);
+
+	lwm2m_get_bool_fake.custom_fake = lwm2m_get_bool_fake_default;
+	lwm2m_sprint_ip_addr_fake.custom_fake = lwm2m_sprint_ip_addr_fake_default;
+	lwm2m_init_message_fake.custom_fake = lwm2m_init_message_fake_default;
+	coap_header_get_code_fake.custom_fake = coap_header_get_code_fake_created;
+	coap_find_options_fake.custom_fake = coap_find_options_do_registration_reply_cb_ok;
+	zassert_true(lwm2m_rd_client_start(&ctx, "Test", 0, lwm2m_event_cb, lwm2m_observe_cb) == 0,
+		     NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REGISTRATION_COMPLETE, 0),
+		     NULL);
+
+	zassert_true(lwm2m_rd_client_pause() == 0, NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_ENGINE_SUSPENDED, 1), NULL);
+
+	zassert_true(lwm2m_rd_client_resume() == 0, NULL);
+	zassert_true(check_lwm2m_rd_client_event(LWM2M_RD_CLIENT_EVENT_REG_UPDATE_COMPLETE, 2),
+		     NULL);
+}
diff --git a/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/src/stubs.c b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/src/stubs.c
new file mode 100644
index 0000000..fe21254
--- /dev/null
+++ b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/src/stubs.c
@@ -0,0 +1,204 @@
+/*
+ * Copyright (c) 2022 grandcentrix GmbH
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/logging/log.h>
+
+#include <stubs.h>
+
+LOG_MODULE_DECLARE(lwm2m_rd_client_test);
+
+/* zephyr/net/coap.h */
+DEFINE_FAKE_VALUE_FUNC(uint8_t, coap_header_get_code, const struct coap_packet *);
+uint8_t coap_header_get_code_fake_created(const struct coap_packet *cpkt)
+{
+	return COAP_RESPONSE_CODE_CREATED;
+}
+uint8_t coap_header_get_code_fake_deleted(const struct coap_packet *cpkt)
+{
+	return COAP_RESPONSE_CODE_DELETED;
+}
+
+DEFINE_FAKE_VALUE_FUNC(int, coap_append_option_int, struct coap_packet *, uint16_t, unsigned int);
+DEFINE_FAKE_VALUE_FUNC(int, coap_packet_append_option, struct coap_packet *, uint16_t,
+		       const uint8_t *, uint16_t);
+int coap_packet_append_option_fake_err(struct coap_packet *cpkt, uint16_t code,
+				       const uint8_t *value, uint16_t len)
+{
+	return -1;
+}
+
+DEFINE_FAKE_VALUE_FUNC(int, coap_packet_append_payload_marker, struct coap_packet *);
+DEFINE_FAKE_VALUE_FUNC(int, coap_find_options, const struct coap_packet *, uint16_t,
+		       struct coap_option *, uint16_t);
+int coap_find_options_do_registration_reply_cb_ok(const struct coap_packet *cpkt, uint16_t code,
+						  struct coap_option *options, uint16_t veclen)
+{
+	char options0[] = "rd";
+	char options1[] = "jATO2yn9u7";
+
+	options[1].len = sizeof(options0);
+	memcpy(&options[1].value, &options0, sizeof(options0));
+	options[1].len = sizeof(options1);
+	memcpy(&options[1].value, &options1, sizeof(options1));
+	return 3;
+}
+
+DEFINE_FAKE_VALUE_FUNC(uint16_t, coap_next_id);
+
+/* zephyr/net/lwm2m.h */
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_engine_start, struct lwm2m_ctx *);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_engine_stop, struct lwm2m_ctx *);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_open_socket, struct lwm2m_ctx *);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_get_u32, const struct lwm2m_obj_path *, uint32_t *);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_get_u16, const struct lwm2m_obj_path *, uint16_t *);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_get_bool, const struct lwm2m_obj_path *, bool *);
+int lwm2m_get_bool_fake_default(const struct lwm2m_obj_path *path, bool *value)
+{
+	*value = false;
+	return 0;
+}
+
+/* subsys/net/lib/lwm2m/lwm2m_engine.h */
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_socket_start, struct lwm2m_ctx *);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_socket_close, struct lwm2m_ctx *);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_close_socket, struct lwm2m_ctx *);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_security_inst_id_to_index, uint16_t);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_engine_connection_resume, struct lwm2m_ctx *);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_push_queued_buffers, struct lwm2m_ctx *);
+DEFINE_FAKE_VOID_FUNC(lwm2m_engine_context_init, struct lwm2m_ctx *);
+DEFINE_FAKE_VOID_FUNC(lwm2m_engine_context_close, struct lwm2m_ctx *);
+DEFINE_FAKE_VALUE_FUNC(char *, lwm2m_sprint_ip_addr, const struct sockaddr *);
+char *lwm2m_sprint_ip_addr_fake_default(const struct sockaddr *addr)
+{
+	return "192.168.1.1:4444";
+}
+
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_server_short_id_to_inst, uint16_t);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_security_index_to_inst_id, int);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_engine_add_service, k_work_handler_t, uint32_t);
+
+k_work_handler_t lwm2m_engine_add_service_service;
+uint32_t lwm2m_engine_add_service_period_ms = 20;
+int lwm2m_engine_add_service_fake_default(k_work_handler_t service, uint32_t period_ms)
+{
+	lwm2m_engine_add_service_service = service;
+	lwm2m_engine_add_service_period_ms = period_ms;
+	return 0;
+}
+
+uint16_t counter = RD_CLIENT_MAX_SERVICE_ITERATIONS;
+struct lwm2m_message *pending_message;
+void *(*pending_message_cb)();
+
+static void service_work_fn(struct k_work *work)
+{
+	while (lwm2m_engine_add_service_service != NULL) {
+		if (pending_message != NULL && pending_message_cb != NULL) {
+			pending_message_cb(pending_message);
+			pending_message = NULL;
+		}
+
+		lwm2m_engine_add_service_service(work);
+		k_sleep(K_MSEC(lwm2m_engine_add_service_period_ms));
+		counter--;
+
+		/* avoid endless loop if rd client is stuck somewhere */
+		if (counter == 0) {
+			break;
+		}
+	}
+}
+
+void wait_for_service(uint16_t cycles)
+{
+	uint16_t end = counter - cycles;
+
+	while (counter > end) {
+		k_sleep(K_MSEC(1));
+	}
+}
+
+K_WORK_DEFINE(service_work, service_work_fn);
+
+void test_lwm2m_engine_start_service(void)
+{
+	counter = RD_CLIENT_MAX_SERVICE_ITERATIONS;
+	k_work_submit(&service_work);
+}
+
+void test_lwm2m_engine_stop_service(void)
+{
+	pending_message_cb = NULL;
+	k_work_cancel(&service_work);
+}
+
+/* subsys/net/lib/lwm2m/lwm2m_message_handling.h */
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_init_message, struct lwm2m_message *);
+int lwm2m_init_message_fake_default(struct lwm2m_message *msg)
+{
+	pending_message = msg;
+	return 0;
+}
+
+void test_prepare_pending_message_cb(void *cb)
+{
+	pending_message_cb = cb;
+}
+
+DEFINE_FAKE_VOID_FUNC(lwm2m_reset_message, struct lwm2m_message *, bool);
+DEFINE_FAKE_VALUE_FUNC(int, lwm2m_send_message_async, struct lwm2m_message *);
+
+/* subsys/net/lib/lwm2m/lwm2m_registry.h */
+DEFINE_FAKE_VOID_FUNC(lwm2m_engine_get_binding, char *);
+DEFINE_FAKE_VOID_FUNC(lwm2m_engine_get_queue_mode, char *);
+
+/* subsys/net/lib/lwm2m/lwm2m_rw_link_format.h */
+FAKE_VALUE_FUNC(int, put_begin, struct lwm2m_output_context *, struct lwm2m_obj_path *);
+FAKE_VALUE_FUNC(int, put_end, struct lwm2m_output_context *, struct lwm2m_obj_path *);
+FAKE_VALUE_FUNC(int, put_begin_oi, struct lwm2m_output_context *, struct lwm2m_obj_path *);
+FAKE_VALUE_FUNC(int, put_end_oi, struct lwm2m_output_context *, struct lwm2m_obj_path *);
+FAKE_VALUE_FUNC(int, put_begin_r, struct lwm2m_output_context *, struct lwm2m_obj_path *);
+FAKE_VALUE_FUNC(int, put_end_r, struct lwm2m_output_context *, struct lwm2m_obj_path *);
+FAKE_VALUE_FUNC(int, put_begin_ri, struct lwm2m_output_context *, struct lwm2m_obj_path *);
+FAKE_VALUE_FUNC(int, put_end_ri, struct lwm2m_output_context *, struct lwm2m_obj_path *);
+FAKE_VALUE_FUNC(int, put_s8, struct lwm2m_output_context *, struct lwm2m_obj_path *, int8_t);
+FAKE_VALUE_FUNC(int, put_s16, struct lwm2m_output_context *, struct lwm2m_obj_path *, int16_t);
+FAKE_VALUE_FUNC(int, put_s32, struct lwm2m_output_context *, struct lwm2m_obj_path *, int32_t);
+FAKE_VALUE_FUNC(int, put_s64, struct lwm2m_output_context *, struct lwm2m_obj_path *, int64_t);
+FAKE_VALUE_FUNC(int, put_time, struct lwm2m_output_context *, struct lwm2m_obj_path *, time_t);
+FAKE_VALUE_FUNC(int, put_string, struct lwm2m_output_context *, struct lwm2m_obj_path *, char *,
+		size_t);
+FAKE_VALUE_FUNC(int, put_float, struct lwm2m_output_context *, struct lwm2m_obj_path *, double *);
+FAKE_VALUE_FUNC(int, put_bool, struct lwm2m_output_context *, struct lwm2m_obj_path *, bool);
+FAKE_VALUE_FUNC(int, put_opaque, struct lwm2m_output_context *, struct lwm2m_obj_path *, char *,
+		size_t);
+FAKE_VALUE_FUNC(int, put_objlnk, struct lwm2m_output_context *, struct lwm2m_obj_path *,
+		struct lwm2m_objlnk *);
+FAKE_VALUE_FUNC(int, put_corelink, struct lwm2m_output_context *, const struct lwm2m_obj_path *);
+
+const struct lwm2m_writer link_format_writer = {
+	.put_begin = put_begin,
+	.put_end = put_end,
+	.put_begin_oi = put_begin_oi,
+	.put_end_oi = put_end_oi,
+	.put_begin_r = put_begin_r,
+	.put_end_r = put_end_r,
+	.put_begin_ri = put_begin_oi,
+	.put_end_ri = put_end_oi,
+	.put_s8 = put_s8,
+	.put_s16 = put_s16,
+	.put_s32 = put_s32,
+	.put_s64 = put_s64,
+	.put_time = put_time,
+	.put_string = put_string,
+	.put_float = put_float,
+	.put_bool = put_bool,
+	.put_opaque = put_opaque,
+	.put_objlnk = put_objlnk,
+	.put_corelink = put_corelink,
+};
+
+DEFINE_FAKE_VALUE_FUNC(int, do_register_op_link_format, struct lwm2m_message *);
diff --git a/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/src/stubs.h b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/src/stubs.h
new file mode 100644
index 0000000..9a87ebf
--- /dev/null
+++ b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/src/stubs.h
@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2022 grandcentrix GmbH
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef STUBS_H
+#define STUBS_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include <zephyr/fff.h>
+#include <zephyr/net/lwm2m.h>
+#include <zephyr/ztest.h>
+
+#include <lwm2m_engine.h>
+
+/* Number of iterations the state machine within the RDClient service
+ * is triggered
+ */
+static const uint8_t RD_CLIENT_MAX_SERVICE_ITERATIONS = 50;
+
+/* zephyr/net/coap.h */
+DECLARE_FAKE_VALUE_FUNC(uint8_t, coap_header_get_code, const struct coap_packet *);
+uint8_t coap_header_get_code_fake_created(const struct coap_packet *cpkt);
+uint8_t coap_header_get_code_fake_deleted(const struct coap_packet *cpkt);
+DECLARE_FAKE_VALUE_FUNC(int, coap_append_option_int, struct coap_packet *, uint16_t, unsigned int);
+DECLARE_FAKE_VALUE_FUNC(int, coap_packet_append_option, struct coap_packet *, uint16_t,
+			const uint8_t *, uint16_t);
+int coap_packet_append_option_fake_err(struct coap_packet *cpkt, uint16_t code,
+				       const uint8_t *value, uint16_t len);
+DECLARE_FAKE_VALUE_FUNC(int, coap_packet_append_payload_marker, struct coap_packet *);
+DECLARE_FAKE_VALUE_FUNC(int, coap_find_options, const struct coap_packet *, uint16_t,
+			struct coap_option *, uint16_t);
+int coap_find_options_do_registration_reply_cb_ok(const struct coap_packet *cpkt, uint16_t code,
+						  struct coap_option *options, uint16_t veclen);
+DECLARE_FAKE_VALUE_FUNC(uint16_t, coap_next_id);
+
+/* zephyr/net/lwm2m.h */
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_engine_start, struct lwm2m_ctx *);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_engine_stop, struct lwm2m_ctx *);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_open_socket, struct lwm2m_ctx *);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_get_u32, const struct lwm2m_obj_path *, uint32_t *);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_get_u16, const struct lwm2m_obj_path *, uint16_t *);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_get_bool, const struct lwm2m_obj_path *, bool *);
+int lwm2m_get_bool_fake_default(const struct lwm2m_obj_path *path, bool *value);
+
+/* subsys/net/lib/lwm2m/lwm2m_engine.h */
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_socket_start, struct lwm2m_ctx *);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_socket_close, struct lwm2m_ctx *);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_close_socket, struct lwm2m_ctx *);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_security_inst_id_to_index, uint16_t);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_engine_connection_resume, struct lwm2m_ctx *);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_push_queued_buffers, struct lwm2m_ctx *);
+DECLARE_FAKE_VOID_FUNC(lwm2m_engine_context_init, struct lwm2m_ctx *);
+DECLARE_FAKE_VOID_FUNC(lwm2m_engine_context_close, struct lwm2m_ctx *);
+DECLARE_FAKE_VALUE_FUNC(char *, lwm2m_sprint_ip_addr, const struct sockaddr *);
+char *lwm2m_sprint_ip_addr_fake_default(const struct sockaddr *addr);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_server_short_id_to_inst, uint16_t);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_security_index_to_inst_id, int);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_engine_add_service, k_work_handler_t, uint32_t);
+int lwm2m_engine_add_service_fake_default(k_work_handler_t service, uint32_t period_ms);
+void wait_for_service(uint16_t cycles);
+void test_lwm2m_engine_start_service(void);
+void test_lwm2m_engine_stop_service(void);
+
+/* subsys/net/lib/lwm2m/lwm2m_message_handling.h  */
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_init_message, struct lwm2m_message *);
+int lwm2m_init_message_fake_default(struct lwm2m_message *msg);
+void test_prepare_pending_message_cb(void *cb);
+
+DECLARE_FAKE_VOID_FUNC(lwm2m_reset_message, struct lwm2m_message *, bool);
+DECLARE_FAKE_VALUE_FUNC(int, lwm2m_send_message_async, struct lwm2m_message *);
+
+/* subsys/net/lib/lwm2m/lwm2m_registry.h */
+DECLARE_FAKE_VOID_FUNC(lwm2m_engine_get_binding, char *);
+DECLARE_FAKE_VOID_FUNC(lwm2m_engine_get_queue_mode, char *);
+
+/* subsys/net/lib/lwm2m/lwm2m_rw_link_format.h */
+DECLARE_FAKE_VALUE_FUNC(int, do_register_op_link_format, struct lwm2m_message *);
+
+#define DO_FOREACH_FAKE(FUNC)                                                                      \
+	do {                                                                                       \
+		FUNC(coap_header_get_code)                                                         \
+		FUNC(coap_append_option_int)                                                       \
+		FUNC(coap_packet_append_option)                                                    \
+		FUNC(coap_packet_append_payload_marker)                                            \
+		FUNC(coap_find_options)                                                            \
+		FUNC(coap_next_id)                                                                 \
+		FUNC(lwm2m_engine_start)                                                           \
+		FUNC(lwm2m_engine_stop)                                                            \
+		FUNC(lwm2m_get_u32)                                                                \
+		FUNC(lwm2m_get_u16)                                                                \
+		FUNC(lwm2m_get_bool)                                                               \
+		FUNC(lwm2m_socket_start)                                                           \
+		FUNC(lwm2m_socket_close)                                                           \
+		FUNC(lwm2m_close_socket)                                                           \
+		FUNC(lwm2m_security_inst_id_to_index)                                              \
+		FUNC(lwm2m_engine_connection_resume)                                               \
+		FUNC(lwm2m_push_queued_buffers)                                                    \
+		FUNC(lwm2m_engine_context_init)                                                    \
+		FUNC(lwm2m_engine_context_close)                                                   \
+		FUNC(lwm2m_sprint_ip_addr)                                                         \
+		FUNC(lwm2m_server_short_id_to_inst)                                                \
+		FUNC(lwm2m_security_index_to_inst_id)                                              \
+		FUNC(lwm2m_engine_add_service)                                                     \
+		FUNC(lwm2m_init_message)                                                           \
+		FUNC(lwm2m_reset_message)                                                          \
+		FUNC(lwm2m_send_message_async)                                                     \
+		FUNC(lwm2m_engine_get_binding)                                                     \
+		FUNC(lwm2m_engine_get_queue_mode)                                                  \
+		FUNC(do_register_op_link_format)                                                   \
+	} while (0)
+
+#endif /* STUBS_H */
diff --git a/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/testcase.yaml b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/testcase.yaml
new file mode 100644
index 0000000..a5af87c
--- /dev/null
+++ b/tests/subsys/net/lib/lwm2m/lwm2m_rd_client/testcase.yaml
@@ -0,0 +1,9 @@
+common:
+  depends_on: netif
+tests:
+  subsys.net.lib.lwm2m_rd_client:
+    tags: net lwm2m
+    platform_allow: native_posix qemu_x86 qemu_x86_64
+    integration_platforms:
+      - native_posix
+      - qemu_x86