Deletion Trigger not working?

Question

I want my trigger to prevent deletion of Account records, the code doesn't show any error but my Account records are still being deleted? here is my code

trigger PreventAccountDelete on Account(before delete){
    for(Account a :[select Id from Account where Id IN:Trigger.old])
    {
        System.debug('Cant delete');
    }

}

Answer 1

In order to prevent delete transaction to be committed to DB, you need to addError to record, that should not be deleted

trigger PreventAccountDelete on Account (before delete) {

    for(Account acc : trigger.old){
        acc.addError('Account Cannot be deleted');
    }
}

to test this behavior run the following unit-test

@isTest
private class PreventAccountDeleteTest {

    @isTest
    static void testPreventAccDel(){
        Account accRecord = new Account(name='testAccount');
        insert accRecord;

        Test.startTest();

        try{
            delete accRecord;
            System.assertEquals(false, 'An Error was expected');
        }catch(DMLexception e){
            System.assertEquals(true, e.getMessage().contains('Account Cannot be deleted'),'Account Cannot be deleted');                       
        }

        Test.stopTest();

    }
}