Sample Code:
Employee__c emp = new Employee__c(Employee_Name__c = 'Testsing');
insert emp;
Test.setCreatedDate(emp.Id, DateTime.newInstance(2000,10,10));
Check the below link for more information
https://developer.salesforce.com/docs/atlas.en-us.200.0.apexcode.meta/apexcode/apex_methods_system_test.htm#apex_System_Test_setCreatedDate
Cheers!!!
Employee__c emp = new Employee__c(Employee_Name__c = 'Testsing');
insert emp;
Test.setCreatedDate(emp.Id, DateTime.newInstance(2000,10,10));
Check the below link for more information
https://developer.salesforce.com/docs/atlas.en-us.200.0.apexcode.meta/apexcode/apex_methods_system_test.htm#apex_System_Test_setCreatedDate
Cheers!!!