Salesforce Trigger Test Class

Question

below is my Apex Trigger. I am a beginner and trying to write its test class but continuously getting error "System.DmlException: Insert failed. First exception on row 0; first error: REQUIRED_FIELD_MISSING, Error: You can't select products until you've chosen a price book for this opportunity on the products related list.: []".

trigger TrgrOptyHighestCustmorePrice on Opportunity (before insert, before update) {

public Id oid;
public String bidType;
public String BUCode;

for(Opportunity o : trigger.new)
{
    oid = o.Id; 
    bidType = o.BidType__c;
    BUCode = o.Business_Line_BU__c;
}

List<OpportunityLineItem> oliList = new list<OpportunityLineItem>([SELECT id, Customer_Price__c, ReCat_Product_Line__c 
                                                               FROM OpportunityLineItem 
                                                               WHERE OpportunityId =: oid ORDER BY 
                                                               Customer_Price__c DESC LIMIT 1]);

for(OpportunityLineItem oli : oliList)
{
    if(bidType == 'Competitive' && oli.ReCat_Product_Line__c == 'DMS')
    {
        BUCode = 'BL.619';
    }
    if(bidType == 'Competitive' && (oli.ReCat_Product_Line__c == 'EMS' || oli.ReCat_Product_Line__c == 'GMS'))
    {
        BUCode = 'BL.620';
    }
    if(bidType == 'Competitive' && oli.ReCat_Product_Line__c == 'MMS')
    {
        BUCode = 'BL.622';
    }
    if(bidType == 'Sole Sourced' && oli.ReCat_Product_Line__c == 'DMS')
    {
        BUCode = 'BL.624';
    }
    if(bidType == 'Sole Sourced' && (oli.ReCat_Product_Line__c == 'EMS' || oli.ReCat_Product_Line__c == 'GMS'))
    {
        BUCode = 'BL.621';
    }
    if(bidType == 'Sole Sourced' && oli.ReCat_Product_Line__c == 'MMS')
    { 
        BUCode = 'BL.623';
    }        
}

for(Opportunity opt : trigger.new)
{
    opt.Business_Line_BU__c = BUCode;        
}    
}

Test Class

@isTest(seeAllData=true)
public class Test_TrgrOptyHighestCustmorePrice {
    private static testmethod void TrgrOptyHighestCustmorePriceTest(){
        Test.startTest();
        //Insert a test product.
        Product2 p1 = new Product2(Name='Product Monthly 1111', isActive=true, CurrencyIsoCode='USD', ReCat_Product_Line__c = 'DMS');
        insert p1; 

        // Get standard price book ID.
        Id pricebookId = Test.getStandardPricebookId();

        // Insert a price book entry for the standard price book.
        PricebookEntry standardPrice = new PricebookEntry(
            Pricebook2Id = pricebookId, Product2Id = p1.Id,
            UnitPrice = 10000, IsActive = true);
        insert standardPrice;

        Pricebook2 customPB = new Pricebook2(Name='Custom Pricebook', isActive=true);
        insert customPB;

        PricebookEntry customPrice = new PricebookEntry(
            Pricebook2Id = customPB.Id, Product2Id = p1.Id,
            UnitPrice = 12000, IsActive = true);
        insert customPrice;

        // Insert Opportunity
        Opportunity opt = new Opportunity(Name='Test',StageName='Prospect', 
                                          CloseDate=date.today(),BidType__c = 'Competitive', 
                                          Business_Line_BU__c = 'BL.619', 
                                          PriceBook2 = customPB);
        insert opt;

        OpportunityLineItem optLI = new OpportunityLineItem(OpportunityId = opt.id, Product2Id = p1.Id);
        insert optLI;
        update opt;
        Test.stopTest();
    }

}

I am unable to understand how can I test my simple trigger.

Answer 1

Its because u do not fill all required fields for the Opportunity Line Item. See: https://developer.salesforce.com/docs/atlas.en-us.api.meta/api/sforce_api_objects_opportunitylineitem.htm for required fields.

This as an example will work:

OpportunityLineItem optLI = new OpportunityLineItem(OpportunityId = opt.id, Product2Id = p1.Id, TotalPrice = 100, PricebookEntryId=customPrice.Id, Quantity =3);