diff --git a/admin/tool/uploadcourse/tests/course_test.php b/admin/tool/uploadcourse/tests/course_test.php
index fd33545a768..a173e721811 100644
--- a/admin/tool/uploadcourse/tests/course_test.php
+++ b/admin/tool/uploadcourse/tests/course_test.php
@@ -35,6 +35,13 @@ global $CFG;
  */
 class tool_uploadcourse_course_testcase extends advanced_testcase {
 
+    /**
+     * Tidy up open files that may be left open.
+     */
+    protected function tearDown() {
+        gc_collect_cycles();
+    }
+
     public function test_proceed_without_prepare() {
         $this->resetAfterTest(true);
         $mode = tool_uploadcourse_processor::MODE_CREATE_NEW;
diff --git a/admin/tool/uploadcourse/tests/processor_test.php b/admin/tool/uploadcourse/tests/processor_test.php
index 1dd20dc1927..2d2ec04456b 100644
--- a/admin/tool/uploadcourse/tests/processor_test.php
+++ b/admin/tool/uploadcourse/tests/processor_test.php
@@ -36,6 +36,13 @@ require_once($CFG->libdir . '/csvlib.class.php');
  */
 class tool_uploadcourse_processor_testcase extends advanced_testcase {
 
+    /**
+     * Tidy up open files that may be left open.
+     */
+    protected function tearDown() {
+        gc_collect_cycles();
+    }
+
     public function test_basic() {
         global $DB;
         $this->resetAfterTest(true);
diff --git a/backup/moodle2/tests/moodle2_test.php b/backup/moodle2/tests/moodle2_test.php
index bb937aa65d5..960c9eca09d 100644
--- a/backup/moodle2/tests/moodle2_test.php
+++ b/backup/moodle2/tests/moodle2_test.php
@@ -38,6 +38,13 @@ require_once($CFG->libdir . '/completionlib.php');
  */
 class core_backup_moodle2_testcase extends advanced_testcase {
 
+    /**
+     * Tidy up open files that may be left open.
+     */
+    protected function tearDown() {
+        gc_collect_cycles();
+    }
+
     /**
      * Tests the availability field on modules and sections is correctly
      * backed up and restored.
diff --git a/course/tests/courselib_test.php b/course/tests/courselib_test.php
index e8c513a127b..8a0e045e75d 100644
--- a/course/tests/courselib_test.php
+++ b/course/tests/courselib_test.php
@@ -33,6 +33,13 @@ require_once($CFG->dirroot . '/tag/lib.php');
 
 class core_course_courselib_testcase extends advanced_testcase {
 
+    /**
+     * Tidy up open files that may be left open.
+     */
+    protected function tearDown() {
+        gc_collect_cycles();
+    }
+
     /**
      * Set forum specific test values for calling create_module().
      *
diff --git a/course/tests/externallib_test.php b/course/tests/externallib_test.php
index 13826b87809..756c626f533 100644
--- a/course/tests/externallib_test.php
+++ b/course/tests/externallib_test.php
@@ -47,6 +47,13 @@ class core_course_externallib_testcase extends externallib_advanced_testcase {
         require_once($CFG->dirroot . '/course/externallib.php');
     }
 
+    /**
+     * Tidy up open files that may be left open.
+     */
+    protected function tearDown() {
+        gc_collect_cycles();
+    }
+
     /**
      * Test create_categories
      */
diff --git a/lib/tests/questionlib_test.php b/lib/tests/questionlib_test.php
index 1b0c2bcfebf..10b4007a031 100644
--- a/lib/tests/questionlib_test.php
+++ b/lib/tests/questionlib_test.php
@@ -51,6 +51,13 @@ class core_questionlib_testcase extends advanced_testcase {
         $this->resetAfterTest();
     }
 
+    /**
+     * Tidy up open files that may be left open.
+     */
+    protected function tearDown() {
+        gc_collect_cycles();
+    }
+
     public function test_question_reorder_qtypes() {
         $this->assertEquals(
             array(0 => 't2', 1 => 't1', 2 => 't3'),
diff --git a/mod/assign/feedback/editpdf/tests/editpdf_test.php b/mod/assign/feedback/editpdf/tests/editpdf_test.php
index 6afe93ffa8b..207a64bd299 100644
--- a/mod/assign/feedback/editpdf/tests/editpdf_test.php
+++ b/mod/assign/feedback/editpdf/tests/editpdf_test.php
@@ -52,6 +52,13 @@ class assignfeedback_editpdf_testcase extends mod_assign_base_testcase {
         parent::setUp();
     }
 
+    /**
+     * Tidy up open files that may be left open.
+     */
+    protected function tearDown() {
+        gc_collect_cycles();
+    }
+
     protected function create_assign_and_submit_pdf() {
         global $CFG;
         $assign = $this->create_instance(array('assignsubmission_onlinetext_enabled' => 1,