Messages going missing in test suite

[Benefits Dragon]

For some reason in one of my test suites messages that are being sent
by one process are not being received by the other.  When I run the
same commands on the console (that includes the same test case setup)
as are in the test it works fine and all messages are received that
should be.

The process is running just before I send the message so it's not that
it doesn't exist and I've put print statements in to make sure it does
get to the line where the message is sent and it prints out my
statement just before I call the process but the second print
statement at the top of my handle_cast function of my implementation
of a gen_server doesn't show (as well as the operations the message
should trigger not being done).  (Also it is an async -> handle_cast
which works normally so I am using the right one).

Anyone ideas what may be wrong or how I might be able to find out?