diff --git a/mod/forum/tests/vaults_post_test.php b/mod/forum/tests/vaults_post_test.php
index 8ac2a182706..787360c1de6 100644
--- a/mod/forum/tests/vaults_post_test.php
+++ b/mod/forum/tests/vaults_post_test.php
@@ -227,38 +227,85 @@ class mod_forum_vaults_post_testcase extends advanced_testcase {
 
         [$student, $otherstudent] = $this->helper_create_users($course, 2, 'student');
         [$teacher, $otherteacher] = $this->helper_create_users($course, 2, 'teacher');
-        [$discussion, $post] = $this->helper_post_to_forum($forum, $teacher);
-        $reply = $this->helper_post_to_discussion($forum, $discussion, $teacher, [
-                'privatereplyto' => $student->id,
-            ]);
+
+        // Create the posts structure below.
+        // Forum:
+        // -> Post (student 1)
+        //   -> Post private reply (teacher 1)
+        // -> Otherpost (teacher 1)
+        //   -> Otherpost private reply (teacher 2)
+        //   -> Otherpost reply (student 1)
+        //     -> Otherpost reply private reply (teacher 1).
+        [$discussion, $post] = $this->helper_post_to_forum($forum, $student);
+        $postprivatereply = $this->helper_reply_to_post($post, $teacher, [
+            'privatereplyto' => $student->id
+        ]);
         [$otherdiscussion, $otherpost] = $this->helper_post_to_forum($forum, $teacher);
+        $otherpostprivatereply = $this->helper_reply_to_post($otherpost, $otherteacher, [
+            'privatereplyto' => $teacher->id,
+        ]);
+        $otherpostreply = $this->helper_reply_to_post($otherpost, $student);
+        $otherpostreplyprivatereply = $this->helper_reply_to_post($otherpostreply, $teacher, [
+            'privatereplyto' => $student->id
+        ]);
 
-        // The user is the author.
+        // Teacher 1. Request all posts from the vault, telling the vault that the teacher CAN see private replies made by anyone.
         $entities = $this->vault->get_from_discussion_ids($teacher, [$discussion->id, $otherdiscussion->id], true);
-        $this->assertCount(3, $entities);
+        $this->assertCount(6, $entities);
         $this->assertArrayHasKey($post->id, $entities); // Order is not guaranteed, so just verify element existence.
-        $this->assertArrayHasKey($reply->id, $entities);
+        $this->assertArrayHasKey($postprivatereply->id, $entities);
         $this->assertArrayHasKey($otherpost->id, $entities);
+        $this->assertArrayHasKey($otherpostprivatereply->id, $entities);
+        $this->assertArrayHasKey($otherpostreply->id, $entities);
+        $this->assertArrayHasKey($otherpostreplyprivatereply->id, $entities);
 
-        // The user is the intended recipient.
+        // Student 1. Request all posts from the vault, telling the vault that the student CAN'T see private replies made by anyone.
+        // Teacher2's private reply to otherpost is omitted.
         $entities = $this->vault->get_from_discussion_ids($student, [$discussion->id, $otherdiscussion->id], false);
-        $this->assertCount(3, $entities);
+        $this->assertCount(5, $entities);
         $this->assertArrayHasKey($post->id, $entities); // Order is not guaranteed, so just verify element existence.
-        $this->assertArrayHasKey($reply->id, $entities);
+        $this->assertArrayHasKey($postprivatereply->id, $entities);
         $this->assertArrayHasKey($otherpost->id, $entities);
+        $this->assertArrayHasKey($otherpostreply->id, $entities);
+        $this->assertArrayHasKey($otherpostreplyprivatereply->id, $entities);
 
-        // The user is another teacher..
+        // Student 1. Request all posts from the vault, telling the vault that student CAN see all private replies made.
+        // The private reply made by teacher 2 to otherpost is now included.
+        $entities = $this->vault->get_from_discussion_ids($student, [$discussion->id, $otherdiscussion->id], true);
+        $this->assertCount(6, $entities);
+        $this->assertArrayHasKey($post->id, $entities); // Order is not guaranteed, so just verify element existence.
+        $this->assertArrayHasKey($postprivatereply->id, $entities);
+        $this->assertArrayHasKey($otherpost->id, $entities);
+        $this->assertArrayHasKey($otherpostprivatereply->id, $entities);
+        $this->assertArrayHasKey($otherpostreply->id, $entities);
+        $this->assertArrayHasKey($otherpostreplyprivatereply->id, $entities);
+
+        // Teacher 2. Request all posts from the vault, telling the vault that teacher2 CAN see all private replies made.
         $entities = $this->vault->get_from_discussion_ids($otherteacher, [$discussion->id, $otherdiscussion->id], true);
+        $this->assertCount(6, $entities);
+        $this->assertArrayHasKey($post->id, $entities); // Order is not guaranteed, so just verify element existence.
+        $this->assertArrayHasKey($postprivatereply->id, $entities);
+        $this->assertArrayHasKey($otherpost->id, $entities);
+        $this->assertArrayHasKey($otherpostprivatereply->id, $entities);
+        $this->assertArrayHasKey($otherpostreply->id, $entities);
+        $this->assertArrayHasKey($otherpostreplyprivatereply->id, $entities);
+
+        // Teacher 2. Request all posts from the vault, telling the vault that teacher2 CANNOT see all private replies made.
+        // The private replies not relating to teacher 2 directly are omitted.
+        $entities = $this->vault->get_from_discussion_ids($otherteacher, [$discussion->id, $otherdiscussion->id], false);
+        $this->assertCount(4, $entities);
+        $this->assertArrayHasKey($post->id, $entities); // Order is not guaranteed, so just verify element existence.
+        $this->assertArrayHasKey($otherpost->id, $entities);
+        $this->assertArrayHasKey($otherpostprivatereply->id, $entities);
+        $this->assertArrayHasKey($otherpostreply->id, $entities);
+
+        // Student 2. Request all posts from the vault, telling the vault that student2 CAN'T see all private replies made.
+        // All private replies are omitted, as none relate to student2.
+        $entities = $this->vault->get_from_discussion_ids($otherstudent, [$discussion->id, $otherdiscussion->id], false);
         $this->assertCount(3, $entities);
         $this->assertArrayHasKey($post->id, $entities); // Order is not guaranteed, so just verify element existence.
-        $this->assertArrayHasKey($reply->id, $entities);
-        $this->assertArrayHasKey($otherpost->id, $entities);
-
-        // The user is a different student.
-        $entities = $this->vault->get_from_discussion_ids($otherstudent, [$discussion->id, $otherdiscussion->id], false);
-        $this->assertCount(2, $entities);
-        $this->assertArrayHasKey($post->id, $entities); // Order is not guaranteed, so just verify element existence.
         $this->assertArrayHasKey($otherpost->id, $entities);
+        $this->assertArrayHasKey($otherpostreply->id, $entities);
     }
 
     /**