Test Apex trigger on Case before update

Question

Im stuck, how can I test the Apex trigger frfing on case before update? Any help appreciated.

Im quite new into this universe so I bear in mind :-) Apex trigger:

trigger CaseEscalationTrigger on Case(before update) 
{
   for(Case c : Trigger.new)
   {   
       if (c.Escalate_to__c != NULL)
       {
           String GroupID = c.Escalate_to__c;
           c.OwnerId = [SELECT Id FROM Group where Type = 'Queue' And Name = :GroupID].id;
           c.Escalate_to__c = '';      
       }     
   }
}

Test Class:

@isTest
public class testEscalateToFunction
{
    public static testmethod void testAll()
    {
        // ContentVersion conv=new ContentVersion();      
        Case c = new Case();
        c.Escalate_to__c = '1. SAP';
        //update c;
        System.assertEquals('', c.Escalate_to__c);        
    }
}

Answer 1

You are on the right track but there are some details to refine:

// Tests are isolated from most org data include Group so need to create one
Group g = new Group(
        Name = '1. SAP',
        DeveloperName = '1. SAP' + System.currentTimeMillis(),
        Type = 'Queue'
        );
insert g;

Case c = new Case();
insert c;

// Can't update unless already inserted
c.Escalate_to__c = '1. SAP';
update c;

// The trigger operates in the database layer so you have to requery to see the result
Case actual = [select Escalate_to__c from Case where Id = :c.Id];
System.assertEquals('', actual.Escalate_to__c);

Once you have your test working you should refactor your trigger as it contains the anti-pattern of a query inside a loop. The general pattern is to collect the set of Escalate_to__c values in a Trigger.new loop first, then query the whole set of id values from Group (single query however many Case objects the trigger fires for) in a map, then loop over Trigger.new again using values from the map.

PS

The refactored trigger would look something like this:

trigger CaseEscalationTrigger on Case (before update) {
    Set<String> groupIds = new Set<String>();
    for (Case c : Trigger.new) {   
        if (c.Escalate_to__c != null) {
            groupIds.add(c.Escalate_to__c);
        }
    }
    if (groupIds.size() > 0) {
        Map<String, Id> groupNamesToIds = new Map<String, Id>();
        for (Group g : [
                select Id, Name
                from Group
                where Id in :groupIds
                ]) {
            groupNamesToIds.put(g.Name, g.Id);
        }
        for (Case c : Trigger.new) {   
            if (c.Escalate_to__c != null) {
                c.OwnerId = groupNamesToIds.get(c.Escalate_to__c);
                c.Escalate_to__c = '';
            }
        }
    }
}