I am trying to create a test for an Apex class that displays how many of a particular item have been sold. I have no trouble creating the Apex class but am having trouble creating the test class. I need to create SO headers in the test class but can not create the SO header and or the SO line. I receive the following error when I try to create the SO header:
System.DmlException: Insert failed. First exception on row 0; first error: FIELD_CUSTOM_VALIDATION_EXCEPTION, Cannot insert a Sales Order Header outside of the Rootstock Package.: 
rstk__sohdr__c custH= new rstk__sohdr__c(rstk__sohdr_custno__c='a9w36000000GpJeAAK'); insert custh;
I receive the error on the execution of the insert statement.
How can I create a Rootstock SO from within a Salesforce Apex class?