IDLE confusion

[MrBlueSky]

Hi, I'm trying to use IDLE to develop My First Python App and my head
hurts...

I've a file called spalvi.py with this in it:
    from Test import *
    firstTest("Mike")

And a file called Test.py with this in it:
    def firstTest(name):
        print "Yo",name

I open spalvi.py with IDLE and Run it.  It says "Yo Mike".
I use the File menu to open Test.py and change the message from "Yo" to
"Hi".
I Run it again.... it still says "Yo Mike"  :-(
I close everything down, open spalvi.py with IDLE and Run it again.  It
says "Hi Mike".

So I'm obviously not using IDLE in the "right" way.  But what *is* the
"right" way, when you're trying to develop using several source files?

John