Re: SetUp functions for multiple test cases
- From: Georg Schmid <gspschmid@xxxxxxxxx>
- Date: Tue, 20 Jan 2009 07:24:49 -0800 (PST)
On Jan 20, 3:57 pm, Roy Smith <r...@xxxxxxxxx> wrote:
In article
<45b0bf56-673c-40cd-a27a-62f9943d9...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Georg Schmid <gspsch...@xxxxxxxxx> wrote:
I've just started working with unittests and already hit a snag. I
couldn't find out how to implement a setup function, that is executed
only _once_ before all of the tests. Specifically, I need this for
testing my database interface, and naturally I don't want to create a
new database in-memory and fill it with example data for every single
test case.
Short answer -- there's no way to do it in the unittest framework.
The True Unit Test Zealots will argue that all tests should be 100%
independent of each other, which means there should be NO common state
between test cases. For that matter, they will also argue that unit tests
should not interface with external resources like databases. And they're
right.
On the other hand, the Real World Test Pragmatists will argue that this is
just not practical in all cases. Real programs have classes which interact
with the outside world, and they need to get tested. You could stub out
the external resource, but that's a lot of work, and may introduce as many
problems as it solves. Sometimes, a big part of what you're testing is
your understanding of the external world (i.e. "does this really work like
it's documented?").
Plus, some operations are just too expensive to do for every test case. I
don't know how long it takes to build your in-memory database. If it takes
one second, it probably makes sense to do it for every test case (unless
you've got thousands of test cases). If it takes 10 minutes, then it makes
sense to do it once and deal with the fact that you're violating True Unit
Test Dogma.
Anyway, do what I do. I run the tests with a:
if __name__ == "__main__":
blah blah
block at the bottom of the test file. Just do your "do once" setup in that
code block and store the result in a global.
You might have your setUp() method re-assign the global to an instance
variable and then your test cases can access it via self.whatever. The
reason for that is if at some point in the future you change your mind and
decide to re-build the database in setUp() for each test, you just have to
change setUp(), not touch the individual test cases.
Thanks, exactly what I needed to know.
.
- References:
- SetUp functions for multiple test cases
- From: Georg Schmid
- Re: SetUp functions for multiple test cases
- From: Roy Smith
- SetUp functions for multiple test cases
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