Hi,

This is the trigger

trigger No_Contacts_Not_Related_to_Account on Task (before insert, before update) {
    List<Task> tList = trigger.new;
    List<Id> idList = new List<Id>();
    for(Task t : tList) {
        if(t.whoId != null) idList.add(t.whoId);
    }
    Map<Id, Contact> cMap = new Map<Id, Contact>([select id, accountId from contact where Id in: idList]);

    List<Task> tList_failed = new List<Task>();
    for(Task t : tList) {
        if(t.whoId != null && t.whatId != null && t.whatId != cMap.get(t.whoId).accountId) tList_failed.add(t);
    }

  if(tList_failed.size() > 0) tList[0].addError('Achtung: Ansprechpartner ist nicht beim ausgewählten Debitor hinterlegt ');
}


And here is the Test class but i get this error message "invalid Parameter value" dont know why.

@isTest
Private class No_Contacts_Not_Related_to_Account_Test {

    static testMethod void testTrigger() {
        // Create test Account
        Account acc = new Account(Name = 'Test Account');
        insert acc;

        // Create test Contact related to Account
        Contact con = new Contact(FirstName = 'Test', LastName = 'Contact', AccountId = acc.Id);
        insert con;

        // Create test Contact not related to Account
        Contact con2 = new Contact(FirstName = 'Test2', LastName = 'Contact2');
        insert con2;

        // Create test Tasks with related and not related Contacts
        Task t1 = new Task(Subject = 'Test Task 1', WhoId = con.Id, WhatId = acc.Id);
        Task t2 = new Task(Subject = 'Test Task 2', WhoId = con2.Id, WhatId = acc.Id);

        Test.startTest();
        // Insert Tasks and verify that the trigger throws an error on t2
        try {
            insert new List<Task>{t1, t2};
            System.assert(false, 'Expected error was not thrown');
        } catch (DmlException e) {
            System.assertEquals('Achtung: Ansprechpartner ist nicht beim ausgewählten Debitor hinterlegt ', e.getMessage());
        }
        Test.stopTest();
    }
}

Need help with this test class

Thank you