ElggUser::addFriend PHP Method

    public function addFriend($friend_guid, $create_river_item = false)
    {
        if (!get_user($friend_guid)) {
            return false;
        }
        if (!add_entity_relationship($this->guid, "friend", $friend_guid)) {
            return false;
        }
        if ($create_river_item) {
            elgg_create_river_item(array('view' => 'river/relationship/friend/create', 'action_type' => 'friend', 'subject_guid' => $this->guid, 'object_guid' => $friend_guid));
        }
        return true;
    }

 public function testFriendSubscriptionRemovedWhenFriendRelationshipDeleted()
 {
     $this->user1->addFriend($this->user2->guid);
     $this->assertTrue($this->user1->isFriendsWith($this->user2->guid));
     elgg_add_subscription($this->user1->guid, 'test', $this->user2->guid);
     $this->assertIsA(check_entity_relationship($this->user1->guid, 'notifytest', $this->user2->guid), ElggRelationship::class);
     $this->user1->removeFriend($this->user2->guid);
     $this->assertFalse($this->user1->isFriendsWith($this->user2->guid));
     $this->assertFalse(check_entity_relationship($this->user1->guid, 'notifytest', $this->user2->guid));
 }