testing codes in erl with running processes

[HP Wei]

I have an erl session, in which there is a process running.

I load a testing module which is unrelated to the running process;
then, 
I type fx(...), without specifying the module name: test:fx(...).
erl tells me so dutifully.
But after a few seconds, the running process also exits
with {badarg...} type of error.

Can the action of testing codes somehow
interfere with a process running in the background ??

-HP