[Python-Dev] PEP: Frequently-requested additional features for the unittest module (original) (raw)

Scott David Daniels Scott.Daniels at Acm.Org
Thu Aug 14 06🔞38 CEST 2008

Ben Finney wrote:

Michael Foord <fuzzyman at voidspace.org.uk> writes:

The full list of changes proposed […] and not shot down was something like: […] assertLessThan assertGreaterThan assertLessThanOrEquals assertGreaterThanOrEquals […] "Brett Cannon" <brett at python.org> writes: Is any of this really necessary? Isn't this the equivalent of assert(a < b)? It seems like the only thing you get out of this is a nicer error message, but ``assert(a < b, 'not %r <= %s' % (a, b))`` is not that complex. And do these cases really come up that often? I would want to see some numbers showing that these are really necessary (in both usage and people even specifying an error message in the first place). Though I'm the champion of this PEP, I'll have to refer to Michael Foord for his reasoning (or reference to others' reasoning) on this. My reasoning goes something like this:

 self.assertLessThan(abs(self.base.method(parm1, parm2) -
                         self.base.nominal), 2.54, 'Within an inch')

vs. distance = self.base.method(parm1, parm2) deviation = self.base.method(parm1, parm2) - self.base.nominal self.assert_(abs(deviation) < 2.54, '%s is %s out of spec (more ' 'than an inch)' % (distance, deviation)

It is not so much the assertion on values in variables, as it is assertions on results of calculations. Unfortunately, my tendency would be to forgo the "within an inch" over extracting the values into locals for the purpose of the test; the tests I'm writing currently focus on the manipulation of hardware for the reader, not on the extraction of data for the purpose of testing. Some of the longer sections are already nearly a couple of pages long; that's how much code it takes to do a coherent operation on this particular hardware. I hate that I am using 2 pages now (half a page per is what I'd prefer), and I'm not willing to bloat the operation with more code. As a result, I implemented my own versions of these asserts (Le, Lt, ...) a year or so ago, and still find them so useful that I'll re-implement them where- ever I am working without similar tests available.

--Scott David Daniels Scott.Daniels at Acm.Org

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