Re: How to write a test with random usage patterns?

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From	Hallvard Breien Furuseth <h.b.furuseth@usit.uio.no>
Newsgroups	comp.programming
Subject	Re: How to write a test with random usage patterns?
Date	Mon, 27 Jul 2015 17:00:19 +0200
Organization	University of Oslo, Norway
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Julio Di Egidio <julio@diegidio.name> writes:
> On Monday, July 27, 2015 at 1:48:18 PM UTC+1, Hallvard Breien Furuseth wrote:

[Rearranging a bit]

>> That is, anti_rand() might output random numbers for a while, then
>> switch to (X,Y,Z, X,Y,Z ...) for a while, and so on.
>
> And so on what?  Is it supposed to generate random numbers or not?
> Indeed, why call it anti_rand and not just rand?  And why not just use
> some library function?  (It is utterly non-trivial to code a decent
> random number generator.)

I do *not* want a random number generator.  I want a random _pattern_
generator.  See the Subject header.  Generate some pattern and output
that, then another, and so on.  Some regular patterns, some half-
randomized.  Or something like that.

>>   switch (anti_rand() % CASES) {
> That is not a good approach: if the range of anti_rand is not an exact
> multiple of the number of cases, you get that some cases are hit more
> frequently than others.  But you'll have to clarify about anti_rand
> before I get to suggest a better approach:

Not quite, but the program must be adapted to anti_rand(), yes.
    
>> I expect someone has dealt with this problem before.
>
> I do use random input for some tests, it may be useful to
> automatically generate a large number of test cases with varying
> input: the only drawback is that tests are not repeatable unless you
> specify a seed for the random number generator.

I expect to output the seed at the beginning of the test, and make the
program deterministic after picking the seed.  Or offer that as an
option, anyway.

-- 
Hallvard

Thread

How to write a test with random usage patterns? Hallvard Breien Furuseth <h.b.furuseth@usit.uio.no> - 2015-07-27 14:48 +0200
  Re: How to write a test with random usage patterns? Julio Di Egidio <julio@diegidio.name> - 2015-07-27 07:19 -0700
    Re: How to write a test with random usage patterns? Hallvard Breien Furuseth <h.b.furuseth@usit.uio.no> - 2015-07-27 17:00 +0200
      Re: How to write a test with random usage patterns? Julio Di Egidio <julio@diegidio.name> - 2015-07-27 08:42 -0700
        Re: How to write a test with random usage patterns? Hallvard Breien Furuseth <h.b.furuseth@usit.uio.no> - 2015-07-28 12:53 +0200
  Re: How to write a test with random usage patterns? Julio Di Egidio <julio@diegidio.name> - 2015-07-27 07:42 -0700
  Re: How to write a test with random usage patterns? Hallvard Breien Furuseth <h.b.furuseth@usit.uio.no> - 2015-07-28 12:55 +0200
  Re: How to write a test with random usage patterns? Richard Heathfield <rjh@cpax.org.uk> - 2015-07-28 12:26 +0100
    Re: How to write a test with random usage patterns? Julio Di Egidio <julio@diegidio.name> - 2015-07-28 05:20 -0700
    Re: How to write a test with random usage patterns? Hallvard Breien Furuseth <h.b.furuseth@usit.uio.no> - 2015-07-28 15:03 +0200
      Re: How to write a test with random usage patterns? Richard Heathfield <rjh@cpax.org.uk> - 2015-07-28 17:17 +0100

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