diff --git a/CHANGELOG.md b/CHANGELOG.md
index 877ff46..609fda1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - provide signal handlers so we shut down properly when INCLUDE_BREAKPAD active
 - send status code and reason in websocket close message
 - dont try to install handler for signal 9 
+- add unit tests for interface down
 
 ## [1.0.2] - 2019-02-08
 - Refactored connection.c and updated corresponding unit tests
diff --git a/src/connection.c b/src/connection.c
index 0aa3369..6ba60fd 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -267,7 +267,7 @@ void start_conn_in_progress (void);
  *  1   shutdown
  *  0    delay taken
 */  
-static int backoff_delay (backoff_timer_t *timer)
+int backoff_delay (backoff_timer_t *timer)
 {
   struct timespec ts;
   int rtn;
diff --git a/tests/test_connection.c b/tests/test_connection.c
index b0ebc39..1adc464 100644
--- a/tests/test_connection.c
+++ b/tests/test_connection.c
@@ -39,6 +39,7 @@ extern void init_expire_timer (expire_timer_t *timer);
 extern int check_timer_expired (expire_timer_t *timer, long timeout_ms);
 extern void init_backoff_timer (backoff_timer_t *timer, int max_count);
 extern int update_backoff_delay (backoff_timer_t *timer);
+extern int backoff_delay (backoff_timer_t *timer);
 extern int init_header_info (header_info_t *header_info);
 extern void free_header_info (header_info_t *header_info);
 extern char *build_extra_hdrs (header_info_t *header_info);
@@ -1040,12 +1041,70 @@ void test_create_nopoll_connection()
 
 }
 
+#define BACKOFF_ERR -1
+#define BACKOFF_SHUTDOWN   1
+#define BACKOFF_DELAY_TAKEN 0
+
+backoff_timer_t test_timer;
+
+void *c()
+{
+  sleep (5);
+  g_shutdown = true;
+  terminate_backoff_delay ();
+  pthread_exit(0);
+  return NULL;
+}
+
+void test_backoff_delay ()
+{
+  int rtn;
+  pthread_t thread_c;
+
+  init_backoff_timer (&test_timer, 5);
+  rtn = backoff_delay (&test_timer); // delay will be 3
+  assert_int_equal (rtn, BACKOFF_DELAY_TAKEN);
+
+  update_backoff_delay (&test_timer);  // delay will be 7
+  pthread_create(&thread_c, NULL, c, NULL);
+  rtn = backoff_delay (&test_timer);  // delay will be 15
+  assert_int_equal (rtn, BACKOFF_SHUTDOWN);
+  g_shutdown = false;
+}
+
 void test_get_interface_down_event()
 {
     assert_false(get_interface_down_event());
     set_interface_down_event();
 }
 
+void *b(void *arg)
+{   
+    sleep(5);
+    if (arg)
+      g_shutdown = true;
+    reset_interface_down_event();
+    pthread_exit(0);
+    return NULL;
+}
+
+void test_wait_while_interface_down()
+{
+  int rtn;
+  pthread_t thread_b;
+
+  set_interface_down_event ();
+  pthread_create(&thread_b, NULL, b, NULL);
+  rtn = wait_while_interface_down ();
+  assert_int_equal (rtn, 0);
+  
+  set_interface_down_event ();
+  pthread_create(&thread_b, NULL, b, &rtn);
+  rtn = wait_while_interface_down ();
+  assert_int_equal (rtn, -1);
+  g_shutdown = false;
+}
+
 void *a()
 {   
     sleep(15);
@@ -1211,6 +1270,8 @@ int main(void)
         cmocka_unit_test(test_connect_and_wait),
         cmocka_unit_test(test_keep_trying),
 	cmocka_unit_test(test_create_nopoll_connection),
+	    cmocka_unit_test (test_backoff_delay),
+	    cmocka_unit_test (test_wait_while_interface_down),
         cmocka_unit_test(test_get_interface_down_event),
         cmocka_unit_test(test_interface_down_retry)
     };