I am looking for help.

I have written a test program for an Apex trigger. The program creates a test account and an opportunity

that is associated with it. The code is shown below:

        // Create a test account for 'Corp Admin'
        Account testAccount = new Account
        (
            Name = 'Test Account',
            Owner = [select username from user where username = 'Corp Admin']
        );
        
        insert testAccount;
        
        // Create a forecast opportunity
        Opportunity testOpp = new Opportunity
        (
            AccountId = testAccount.ID,
            Name = 'testOpportunity' + date.today(),
            CloseDate = date.today() + 1,                    
            StageName = 'Contract signed; waiting for P.O',
            Type = 'Existing Business',
            Pricebook2Id = [select Id from Pricebook2 where name = 'Standard Price Book'],
            OwnerId = testAccount.OwnerId
         );
         
         insert testOpp;
         

 In the program, I want to set the appropriate Price Book, so that I can later enter line items from a specific price book.

The line:

Pricebook2Id = [select Id from Pricebook2 where name = 'Standard Price Book']

is used for this purpose.

When compiling, I get the error:

Invalid initial expression type for field Opportunity.Pricebook2Id, expecting: Id.

How would I get the Id for the price book?

In the same way, I am using the following, to enter a line item (OpportunityLineItem) for the opportunity:

PricebookEntryId = [select Id from Product2 where name = 'AC02'],

I get the same kind of error.

         Thanks,

                aqueller