Path: csiph.com!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder1.enfer-du-nord.net!feeds.phibee-telecom.net!newsfeed.xs4all.nl!newsfeed5.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
Return-Path: <ethan@stoneleaf.us>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.001
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'test,': 0.05; 'tests.': 0.07; 'from:addr:ethan': 0.09; 'from:addr:stoneleaf.us': 0.09; 'from:name:ethan furman': 0.09; 'message-id:@stoneleaf.us': 0.09; 'received:184.172': 0.09; 'received:gator410.hostgator.com': 0.09; '~ethan~': 0.09; 'cc:addr:python-list': 0.15; 'exception.': 0.16; 'obsolete': 0.16; 'raises': 0.16; 'received:72.11': 0.16; 'received:72.11.125': 0.16; 'received:72.11.125.166': 0.16; 'subject:instance': 0.16; 'subject:type': 0.16; 'subject:unittest': 0.16; 'test".': 0.16; 'to:addr:pearwood.info': 0.16; 'to:addr:steve+comp.lang.python': 0.16; "to:name:steven d'aprano": 0.16; 'so.': 0.16; 'argument': 0.18; 'changes': 0.19; 'fix': 0.20; 'wrote:': 0.21; '(not': 0.22; 'detect': 0.22; 'fine,': 0.22; 'passing': 0.22; 'header:In-Reply-To:1': 0.22; 'header:User-Agent:1': 0.23; 'right.': 0.23; 'test': 0.24; 'cc:no real name:2**0': 0.26; 'cc:addr:python.org': 0.27; 'subject:with': 0.28; 'code': 0.29; 'decide': 0.29; 'raise': 0.30; 'tests': 0.30; 'cc:2**0': 0.31; 'leave': 0.34; 'too': 0.35; 'two': 0.35; 'should': 0.35; 'explain': 0.35; 'actually': 0.35; 'but': 0.36; 'does': 0.36; 'and/or': 0.37; 'being': 0.39; 'how': 0.40; 'nor': 0.60; 'single': 0.61; 'received:userid': 0.61; 'more': 0.63; 'personal': 0.65; 'remove': 0.65; 'believe': 0.67; 'due': 0.68; 'decision': 0.69; 'approach,': 0.84; 'finely': 0.84; 'so:': 0.84
Date: Fri, 30 Mar 2012 10:45:39 -0700
From: Ethan Furman <ethan@stoneleaf.us>
User-Agent: Thunderbird 1.5.0.10 (Windows/20070221)
MIME-Version: 1.0
To: Steven D'Aprano <steve+comp.lang.python@pearwood.info>
Subject: Re: unittest: assertRaises() with an instance instead of a type
References: <pncb49-ur7.ln1@satorlaser.homedns.org>	<4f735345$0$29981$c3e8da3$5496439d@news.astraweb.com>	<eced49-sge.ln1@satorlaser.homedns.org> <4f751e31$0$29981$c3e8da3$5496439d@news.astraweb.com>
In-Reply-To: <4f751e31$0$29981$c3e8da3$5496439d@news.astraweb.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-AntiAbuse: This header was added to track abuse, please include it with any abuse report
X-AntiAbuse: Primary Hostname - gator410.hostgator.com
X-AntiAbuse: Original Domain - python.org
X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
X-AntiAbuse: Sender Address Domain - stoneleaf.us
X-BWhitelist: no
X-Source: 
X-Source-Args: 
X-Source-Dir: 
X-Source-Sender: mail.admailinc.com ([192.168.10.136]) [72.11.125.166]:2585
X-Source-Auth: ethan+stoneleaf.us
X-Email-Count: 1
X-Source-Cap: dG9idWs7dG9idWs7Z2F0b3I0MTAuaG9zdGdhdG9yLmNvbQ==
Cc: python-list@python.org
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <http://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <http://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.1153.1333132489.3037.python-list@python.org>
Lines: 27
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1333132489 news.xs4all.nl 6911 [2001:888:2000:d::a6]:46282
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:22389

Steven D'Aprano wrote:
> To the degree that the decision of how finely to slice tests is a matter 
> of personal judgement and/or taste, I was wrong to say "that is not the 
> right way". I should have said "that is not how I would do that test".
> 
> I believe that a single test is too coarse, and three or more tests is 
> too fine, but two tests is just right. Let me explain how I come to that 
> judgement.
> 
> If you take a test-driven development approach, the right way to test 
> this is to write testFooWillFail once you decide that foo() should raise 
> MyException but before foo() actually does so. You would write the test, 
> the test would fail, and you would fix foo() to ensure it raises the 
> exception. Then you leave the now passing test in place to detect 
> regressions.
> 
> Then you do the same for the errorcode. Hence two tests.

[snip]

> So: never remove tests just because they are redundant. Only remove them 
> when they are obsolete due to changes in the code being tested.

Very persuasive argument -- I now find myself disposed to writing two 
tests (not three, nor five ;).

~Ethan~