diff --git a/admin/tool/monitor/tests/eventobservers_test.php b/admin/tool/monitor/tests/eventobservers_test.php
index 9239e16e55a..a1cb38423da 100644
--- a/admin/tool/monitor/tests/eventobservers_test.php
+++ b/admin/tool/monitor/tests/eventobservers_test.php
@@ -384,7 +384,7 @@ class tool_monitor_eventobservers_testcase extends advanced_testcase {
             // Now let us trigger 7 instances of the event.
             $event = \mod_book\event\course_module_instance_list_viewed::create_from_course($course);
             $event->trigger();
-            sleep(1); // Add a second delay, to prevent time collisions.
+            $this->waitForSecond(); // Add a second delay, to prevent time collisions.
         }
         $this->run_adhock_tasks();
         $messages = $messagesink->get_messages();
diff --git a/lib/phpunit/classes/advanced_testcase.php b/lib/phpunit/classes/advanced_testcase.php
index 7ee75ebf374..096fe8a0c97 100644
--- a/lib/phpunit/classes/advanced_testcase.php
+++ b/lib/phpunit/classes/advanced_testcase.php
@@ -607,4 +607,17 @@ abstract class advanced_testcase extends base_testcase {
             }
         }
     }
+
+    /**
+     * Wait for a second to roll over, ensures future calls to time() return a different result.
+     *
+     * This is implemented instead of sleep() as we do not need to wait a full second. In some cases
+     * due to calls we may wait more than sleep() would have, on average it will be less.
+     */
+    public function waitForSecond() {
+        $starttime = time();
+        while (time() == $starttime) {
+            usleep(50000);
+        }
+    }
 }
diff --git a/lib/phpunit/tests/advanced_test.php b/lib/phpunit/tests/advanced_test.php
index cf00787a6ab..bca2d378cc8 100644
--- a/lib/phpunit/tests/advanced_test.php
+++ b/lib/phpunit/tests/advanced_test.php
@@ -358,7 +358,7 @@ class core_phpunit_advanced_testcase extends advanced_testcase {
 
         $this->setCurrentTimeStart();
         $this->assertTimeCurrent(time());
-        sleep(2);
+        $this->waitForSecond();
         $this->assertTimeCurrent(time());
         $this->assertTimeCurrent(time()-1);
 
diff --git a/lib/tests/coursecatlib_test.php b/lib/tests/coursecatlib_test.php
index d930044d676..7809595538c 100644
--- a/lib/tests/coursecatlib_test.php
+++ b/lib/tests/coursecatlib_test.php
@@ -236,7 +236,7 @@ class core_coursecatlib_testcase extends advanced_testcase {
         $timecreated = $category1->timemodified;
         $this->assertSame('Cat1', $category1->name);
         $this->assertTrue(empty($category1->description));
-        sleep(2);
+        $this->waitForSecond();
         $testdescription = 'This is cat 1 а также русский текст';
         $category1->update(array('description' => $testdescription));
         $this->assertSame($testdescription, $category1->description);
diff --git a/mod/assign/tests/lib_test.php b/mod/assign/tests/lib_test.php
index 66cabaf38be..34e52194a15 100644
--- a/mod/assign/tests/lib_test.php
+++ b/mod/assign/tests/lib_test.php
@@ -72,7 +72,7 @@ class mod_assign_lib_testcase extends mod_assign_base_testcase {
         $assign->testable_apply_grade_to_user($data, $this->students[0]->id, 0);
 
         // This is required so that the submissions timemodified > the grade timemodified.
-        sleep(2);
+        $this->waitForSecond();
 
         // Edit the submission again.
         $this->setUser($this->students[0]);
@@ -80,7 +80,7 @@ class mod_assign_lib_testcase extends mod_assign_base_testcase {
         $assign->testable_update_submission($submission, $this->students[0]->id, true, false);
 
         // This is required so that the submissions timemodified > the grade timemodified.
-        sleep(2);
+        $this->waitForSecond();
 
         // Allow the student another attempt.
         $this->teachers[0]->ignoresesskey = true;
diff --git a/mod/assign/tests/locallib_test.php b/mod/assign/tests/locallib_test.php
index 0118581b50a..1918d3dc613 100644
--- a/mod/assign/tests/locallib_test.php
+++ b/mod/assign/tests/locallib_test.php
@@ -822,7 +822,7 @@ class mod_assign_locallib_testcase extends mod_assign_base_testcase {
         $plugin->save($submission, $data);
 
         // Wait 1 second so the submission and grade do not have the same timemodified.
-        sleep(1);
+        $this->waitForSecond();
         // Simulate adding a grade.
         $this->setUser($this->teachers[0]);
         $data = new stdClass();