Re: struct or class
On Feb 1, 9:32 pm, Ian Collins <ian-n...@hotmail.com> wrote:
On 02/ 1/11 11:44 AM, James Kanze wrote:
On Jan 29, 4:36 pm, Ian Collins<ian-n...@hotmail.com> wrote:
On 01/29/11 02:11 PM, James Kanze wrote:
So how do you know what the test should do? And tests are
certainly not documentation; they're generally even less
readable than the sources, they only treat specific cases, not
the general rules, and they don't provide a necessary overview.
I don't see how you can say something that unambiguously
states what the unit under test must do isn't documentation.
Prose is open to misinterpretation, code isn't.
Show me a test suite that unambiguously states that the result
of some floating point function must be accurate to 1/2LSB.
Show me a test suite that unambiguously specifies the
requirements that client code must meet in order to use the
class safely in a multithreaded environment.
Well obviously you can't, but as you say else-thread, these
are special cases.
It depends on the application. Where I'm working now, floating
point arithmetic isn't exactly a special case.
For that matter,
show me a test suite that unambiguously specifies the
preconditions a client must meet, or face undefined behavior.
Again, I wouldn't attempt to define those conditions with tests.
But it's essential to document them, if anyone else is to be
able to use your functions.
I could show you many thousands of tests that unambiguously
describe the logic of the code they are testing. Such tests
are good examples of how to use the code being tested. They
also have one huge advantage over prose: they are always up to
date!
Would you argue that examples aren't a form of documentation?
I'm not arguing that examples can't be used in the
documentation; they're a valid part of the documentation in many
cases. I'm arguing that just examples isn't sufficient and
complete documentation, and that test cases aren't always good
examples: for one thing, the set of test cases should contain
a lot more calls than you'd need, and that a reader might
possibly want to read, to explain the behavior, and for the
other, there are some things (like constraints or accuracy
guarantees) that they really can't document: examples, whether
from test cases or not, aren't sufficient.
--
James Kanze
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