[Python-ideas] hookable assertions - to support testing utilities and debugging (original) (raw)

Georg Brandl g.brandl at gmx.net
Thu Feb 19 19:49:02 CET 2015

On 02/19/2015 01:55 PM, Donald Stufft wrote:

So from my perspective (being one of the aforementioned C programmers), I see this question as not so much about the assert statement per se, but rather a more philosophical question:

* is testing code categorically different from production code? * if yes, should assert statements be handled differently in testing code? * if yes, how should that difference be communicated to readers and to the interpreter? (FWIW, I'm personally inclined to answer the first two questions with "yes", but haven't got any ideas as far as the third one goes) Making the behaviour of assert statements configurable attempts to duck those questions instead of answering them, so I don't see at as a particularly useful approach - it makes the language more complex without providing additional clarity, rather than figuring out how to encode a genuinely important categorical distinction between test code and production code into the design of the language. Speaking as a not C programmer, I think the answers to the first two are absolutely yes, and the third one I dunno, maybe some sort of top level import like from testing import realassert or something. I absolutely hate the unittest style of assertFoo, it’s a whole bunch of methods that I can never remember the names of and I have to go look them up. I think using the assert statement is completely logical for test code and I believe you can see this by the fact all of the methods to do checks in unittest are named “assert something”. I think it introduces extra cognitive burden for new users to have to use a whole bunch of additional methods to do assertions in tests TBH. The way py.test works composes nicely with the same kinds of expressions that you’re going to need to learn to write any meaningful Python, but the assertFoo methods are special cases that don’t.

+1

Georg

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