/// <summary>
        ///     Remove a tester
        /// </summary>
        /// <param name="testerToDelete"></param>
        public void RemoveTester(Tester testerToDelete)
        {
            if (XML.GetAllTestersFromXml(_testersXml).All(x => x.Id != testerToDelete.Id))
            {
                throw new Exception("Tester doesn't exist");
            }

            _testersXml.Elements().First(x => x.Element("id")?.Value == testerToDelete.Id.ToString()).Remove();
            _testersXml.Save(Configuration.TestersXmlFilePath);
            _testerChanged = true;
        }
        /// <summary>
        ///     Add tester
        /// </summary>
        /// <param name="newTester"></param>
        public void AddTester(Tester newTester)
        {
            if (XML.GetAllTestersFromXml(_testersXml).Any(tester => tester.Id == newTester.Id))
            {
                throw new Exception("The tester already exist in the system");
            }

            _testersXml.Add(XML.TesterToXmlElement(newTester));
            _testersXml.Save(Configuration.TestersXmlFilePath);
            _testerChanged = true;
        }
        /// <summary>
        ///     DalImp c-tor
        /// </summary>
        internal DalImp()
        {
            try
            {
                //initialize trainees
                if (File.Exists(Configuration.TraineesXmlFilePath))
                {
                    _traineesXml = XElement.Load(Configuration.TraineesXmlFilePath);
                }
                else
                {
                    _traineesXml = new XElement("trainees");
                }
                _trainees = XML.GetAllTraineesFromXml(_traineesXml).ToList();

                //initialize testers
                if (File.Exists(Configuration.TestersXmlFilePath))
                {
                    _testersXml = XElement.Load(Configuration.TestersXmlFilePath);
                }
                else
                {
                    _testersXml = new XElement("testers");
                }
                _testers = XML.GetAllTestersFromXml(_testersXml).ToList();

                //initialize tests
                if (File.Exists(Configuration.TestsXmlFilePath))
                {
                    _tests = XML.DeSerializeTestFromXml().ToList();
                }
                else
                {
                    _tests = new List <Test>();
                }

                //Load configurations
                _config = XML.LoadConfigurations();
            }
            catch
            {
                //do nothing
            }
        }