setting a buffer's namespace

[James Mckernon]

I'm writing a racket module in a certain file. I would like to be able
to test and eval the definitions in this module with some
interactively-evaluated code, a bit like one would in the repl, but
with code saved in another file, so I don't have to type it out each
time.

In the repl this works because one can set the repl's namespace. Is it
possible to set a file buffer to eval its statements in another
module's namespace, or for two file buffers to share a namespace? (And
if it isn't possible, how hard would it be to hack into geiser?)

Of course, using 'require' to load the definitions from the module
file makes them available in my testing file, but this only loads them
the first time. I would like to be able to load the module, test the
files, tinker with the definitions, re-test, re-tinker, etc. This
workflow doesn't work that well if I have to restart the racket
process every time I want to redefine something. I tinkered a little
bit with enter! and dynamic-rerequire, but couldn't get them to behave
as I would like. I'm new to racket and don't really understand the
module system yet, so my apologies if I am overlooking an obvious
solution to this issue there.

Many thanks,
James