Test Class – Error: Compile Error: Field is not writeable: Opportunity.ConnectionReceivedId

I have a re-parenting trigger that fires if the connectionReceivedId is of a certain value. The sad part is that it looks like that field is not writeable, so testing is not possible. I know I could rewrite the trigger to work around this, but I would enjoy being able to actually sort records needing re-parenting by the connection from which they were received.