[SalesForce] How to share a record with a community user

Customer Communities users do not have access to the full sharing model and therefore can't be added on a __Share record. The only way to share a record with a Customer Communities user is through Sharing Sets and Sharing Groups.

Try the Below code to create OpportunityLineItem and everything related to it in Test class.

Product2 prod = new Product2(Name = 'Laptop X200', Family = 'Hardware');
insert prod;

Id pricebookId = Test.getStandardPricebookId();

PricebookEntry standardPrice = new PricebookEntry(Pricebook2Id = pricebookId, Product2Id = prod.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 = prod.Id, UnitPrice = 12000, IsActive = true);
insert customPrice;

Account acc = new Account(Name='TestAccount');
insert acc;

Opportunity opp = new Opportunity(Name='TestOpportunity', AccountId=acc.Id, CloseDate=Date.Today(), StageName='Suspect', Pricebook2Id=customPB.Id);
insert opp;

OpportunityLineItem oli = new OpportunityLineItem(OpportunityId = opp.Id, Quantity = 5, PricebookEntryId = customPrice.Id, TotalPrice = 500);
insert oli;

Hope this will solve the Issue as this is the Best way to create a OpportunityLineItem.