Testing an extension against multiple versions of Postgresql

Greetings All,

I have both postgresql versions 10 and 11 installed on my box. I'm working
on an extension and just realized that 'make install' installs the
extension to the 11 server, but 'make installcheck' runs against the 10
server (I had previously installed the extension there).

Running psql without specifying a host or port connects me to the 10
server, so I suspect that both make installcheck and psql are doing similar
things with respect to connecting to a default server.

So the questions are:
Can I have make install & make installcheck run against multiple versions
at the same time or how do I tell the installcheck to run against the 11
server.

Thanks.

Rhys
Peace & Love | Live Long & Prosper