Elgg\PersistentLoginService::getUserFromHash PHP Method

    public function getUserFromHash($hash)
    {
        if (!$hash) {
            return null;
        }
        $hash = $this->db->sanitizeString($hash);
        $query = "SELECT guid FROM {$this->table} WHERE code = '{$hash}'";
        try {
            $user_row = $this->db->getDataRow($query);
        } catch (\DatabaseException $e) {
            return $this->handleDbException($e);
        }
        if (!$user_row) {
            return null;
        }
        $user = call_user_func($this->_callable_get_user, $user_row->guid);
        return $user ? $user : null;
    }

 function testGettingMissingUserFromKnownHashReturnsNull()
 {
     $this->dbMock->expects($this->once())->method('getDataRow')->will($this->returnValue((object) array('guid' => 234)));
     $user = $this->svc->getUserFromHash($this->mockHash);
     $this->assertNull($user);
 }