improve tests

- add additional pre-check to narrow down a test problem
- run a test in separate processes to be compatible with newer moodle releases

tests/lib_test.php

@@ -81,6 +81,7 @@ public function data_provider_for_test_delete_complex_instance() {
     }
 
     /**
+     * @runInSeparateProcess
      * @dataProvider data_provider_for_test_delete_complex_instance
      */
     public function test_delete_complex_instance($withAttempt) {
@@ -162,6 +163,12 @@ public function test_delete_instance_failure_due_to_question_deletion_failure()
         // Make the method throw an exception
         $mockRepo->shouldReceive('delete_question_by_id')->andThrow(new Exception('Could not delete'));
 
+        // verify created elements before deletion
+        $this->assertCount(1, $DB->get_records('adleradaptivity'));
+        $this->assertCount(2, $DB->get_records('adleradaptivity_tasks'));
+        $this->assertCount(1, $DB->get_records('adleradaptivity_questions'));
+        $this->assertCount(1, $DB->get_records('adleradaptivity_attempts'));
+
         // Try to delete the complex instance.
         $result = adleradaptivity_delete_instance($complex_adleradaptivity_module['module']->id);