Hi Team,

My test classes are failing due to a custom validation rule.

VALIDATION RULE:
(Price_Book_Exist__c = false) && NOT(ISNEW())

I am getting below error: 
System.DmlException: Insert failed. First exception on row 0; first error: CANNOT_EXECUTE_FLOW_TRIGGER, We can't save this record because the “Deactivate Product if changed” process failed. Give your Salesforce admin these details. This error occurred when the flow tried to update records: FIELD_CUSTOM_VALIDATION_EXCEPTION: Custom Price book must be added to the product to proceed further. You can look up ExceptionCode values in the SOAP API Developer Guide.: []

Please find my one APEX CLASS and it's TEST CLASS.

APEX CLASS:

global with sharing class CreatePriceBookClass {
    private static boolean run = true;
    public static boolean runOnce(){
        if(run){
            run=false;
            return true;
        }else{
            return run;
        }
    }
    
    public static void createPriceBook(Product2 product){
        List<Pricebook2> pbs = [SELECT Id,IsStandard FROM Pricebook2 WHERE IsStandard = TRUE];
        
        for(Pricebook2 pb : pbs) { PriceBookEntry pbe1 = new PriceBookEntry();
            pbe1.Pricebook2Id = pb.Id;
            pbe1.Product2Id = product.Id;
            pbe1.UnitPrice = 0;
            pbe1.CurrencyIsoCode = product.CurrencyIsoCode;
            pbe1.IsActive = true;
            insert pbe1;
        }
        List<Pricebook2> pb2s = new List<Pricebook2>();
        if(product.CurrencyIsoCode!= null && product.CurrencyIsoCode.indexOf('USD') >= 0){
            pb2s = [SELECT Id,IsStandard FROM Pricebook2 WHERE Name = 'USD'];
        } else if(product.CurrencyIsoCode!= null && product.CurrencyIsoCode.indexOf('CAD') >= 0){
            pb2s = [SELECT Id,IsStandard FROM Pricebook2 WHERE Name = 'CAD'];
        } else if(product.CurrencyIsoCode!= null && product.CurrencyIsoCode.indexOf('GBP') >= 0){
            pb2s = [SELECT Id,IsStandard FROM Pricebook2 WHERE Name = 'GBP'];
        }
        for(Pricebook2 pb2 : pb2s) {
            PriceBookEntry pbe2 = new PriceBookEntry();
            pbe2.Pricebook2Id = pb2.Id;
            pbe2.Product2Id = product.Id;
            pbe2.UnitPrice = 0;
            pbe2.CurrencyIsoCode = product.CurrencyIsoCode;
            pbe2.IsActive = true;
            pbe2.UseStandardPrice = false;
            insert pbe2;
        }
    }
}

TEST CLASS:

@isTest(seeAllData=false)
public class CreatePriceBookClassTest {

    @TestSetup 
    static void doSetup(){
        TestDataUtility.createTriggerFlag();        

        List<Account> accs = TestDataUtility.createAccounts(3);
        accs[1].vertical__c = 'Mortgage';
        accs[2].vertical__c = 'Personal Loans';
        update accs;
        
        List<Product2> prods = TestDataUtility.createProducts(1,accs[0].Id);
        Id pricebookId  =Test.getStandardPricebookId();
       }
    
    @isTest
    public static void basicTest(){
        List<Product2> prods = [SELECT Id,Lightbox_Pricing__c,CurrencyIsoCode FROM Product2];
       
        for(Product2 prod : prods) {
            Id pricebookId  =Test.getStandardPricebookId();
            PricebookEntry standardPrice = new PricebookEntry();
            standardPrice.Pricebook2Id = pricebookId;
            standardPrice.Product2Id = prod.Id;
            standardPrice.UnitPrice = 1; 
            standardPrice.IsActive = true;
            standardPrice.UseStandardPrice = false;
            insert standardPrice;
            
            Pricebook2 customPB = new Pricebook2();
            customPB.Name='Custom Pricebook';
            customPB.isActive=true;
            insert customPB;
            
            Pricebook2 customPB1 = new Pricebook2();
            customPB1.Name='USD';
            customPB1.isActive=true;
            insert customPB1;
            
            PriceBookEntry pbe = new PriceBookEntry();
            pbe.Pricebook2Id = customPB.Id;
            pbe.Product2Id = prod.Id;
            pbe.UnitPrice = 0;
            pbe.UseStandardPrice = false;
            pbe.CurrencyIsoCode = prod.CurrencyIsoCode;
            pbe.IsActive = true;
            insert pbe;
        
        
            prod.Activated_End_Date__c = System.today();
            update prod;
            CreatePriceBookClass.createPriceBook(prod);
        }
    }
    
    @isTest
    public static void basicCADTest(){
        List<Product2> prods = [SELECT Id,Lightbox_Pricing__c,CurrencyIsoCode FROM Product2];
       
        for(Product2 prod : prods) {
            prod.CurrencyIsoCode = 'CAD';
            Id pricebookId  =Test.getStandardPricebookId();
            PricebookEntry standardPrice = new PricebookEntry();
            standardPrice.Pricebook2Id = pricebookId;
            standardPrice.Product2Id = prod.Id;
            standardPrice.UnitPrice = 1; 
            standardPrice.IsActive = true;
            standardPrice.UseStandardPrice = false;
            standardPrice.CurrencyIsoCode = prod.CurrencyIsoCode;
            insert standardPrice;
            
            Pricebook2 customPB = new Pricebook2();
            customPB.Name='Custom Pricebook';
            customPB.isActive=true;
            insert customPB;
            
            Pricebook2 customPB1 = new Pricebook2();
            customPB1.Name='CAD';
            customPB1.isActive=true;
            insert customPB1;
            
            PriceBookEntry pbe = new PriceBookEntry();
            pbe.Pricebook2Id = customPB.Id;
            pbe.Product2Id = prod.Id;
            pbe.UnitPrice = 0;
            pbe.UseStandardPrice = false;
            pbe.CurrencyIsoCode = prod.CurrencyIsoCode;
            pbe.IsActive = true;
            insert pbe;
        
        
            prod.Activated_End_Date__c = System.today();
            update prod;
            CreatePriceBookClass.createPriceBook(prod);
        }
    }
    
    @isTest
    public static void basicGBPTest(){
        List<Product2> prods = [SELECT Id,Lightbox_Pricing__c,CurrencyIsoCode FROM Product2];
       
        for(Product2 prod : prods) {
            prod.CurrencyIsoCode = 'GBP';
            Id pricebookId  =Test.getStandardPricebookId();
            PricebookEntry standardPrice = new PricebookEntry();
            standardPrice.Pricebook2Id = pricebookId;
            standardPrice.Product2Id = prod.Id;
            standardPrice.UnitPrice = 1; 
            standardPrice.IsActive = true;
            standardPrice.UseStandardPrice = false;
            standardPrice.CurrencyIsoCode = prod.CurrencyIsoCode;
            insert standardPrice;
            
            Pricebook2 customPB = new Pricebook2();
            customPB.Name='Custom Pricebook';
            customPB.isActive=true;
            insert customPB;
            
            Pricebook2 customPB1 = new Pricebook2();
            customPB1.Name='GBP';
            customPB1.isActive=true;
            insert customPB1;
            
            PriceBookEntry pbe = new PriceBookEntry();
            pbe.Pricebook2Id = customPB.Id;
            pbe.Product2Id = prod.Id;
            pbe.UnitPrice = 0;
            pbe.UseStandardPrice = false;
            pbe.CurrencyIsoCode = prod.CurrencyIsoCode;
            pbe.IsActive = true;
            insert pbe;
        
        
            prod.Activated_End_Date__c = System.today();
            update prod;
            CreatePriceBookClass.createPriceBook(prod);
        }
    }
 
}

Please help in solving this issue.

Thank You,
Mahesh