From: Intransition <transfire@...>
Date: 2010-11-05T03:56:21+09:00
Subject: Re: true! or false!



On Nov 4, 1:31 pm, Josh Cheek <josh.ch...@gmail.com> wrote:
> On Thu, Nov 4, 2010 at 5:55 AM, Intransition <transf...@gmail.com> wrote:
> > Making good use of polymorphism I had this idea for assertion methods:
>
> >  class TrueClass
> >    # Assert true.
> >    #
> >    #   (x == y).true!
> >    #
> >    def true!
> >      true
> >    end
> >    # Assert false.
> >    #
> >    #   (x == y).false!
> >    #
> >    def false!
> >      raise "not false!"
> >    end
> >  end
>
> >  class FalseClass
> >    # Assert true.
> >    #
> >    #   (x == y).true!
> >    #
> >    def true!
> >      raise "not true!"
> >    end
> >    # Assert false.
> >    #
> >    #   (x == y).false!
> >    #
> >    def false!
> >      true
> >    end
> >  end
>
> > If only the error message could say something about WHAT was not true
> > or false, this could be pretty nifty.
>
> You would need to override at a higher level, I think, because I frequently
> use object/nil instead of true/false.

Could add the methods to NilClass too.

> require 'test/unit'
>
> class Object
>   def true!   ;  self || raise("not true!")   ;  end
>   def false!  ;  self && raise("not false!")  ;  end
> end

Hmm... Yes, that might be better b/c then anything other then false
and nil will evaluate as true too. That is a good thing, right?

> class TrueBangFalseBang < Test::Unit::TestCase
>   def test_object       ;  [1,2,3][2].true!   ;  end
>   def test_non_object   ;  [1,2,3][3].false!  ;  end
>   def test_true         ;  (1==1).true!       ;  end
>   def test_false        ;  (1==2).false!      ;  end
> end
>
> I like it, except that it doesn't count these as assertions. Even if you mix
> the assertions module into object and use the assert methods, like this:
>
> class Object
>   include Test::Unit::Assertions
>   def true!   ;  assert self   ;  end
>   def false!  ;  assert !self  ;  end
> end
>
> You would get results like "4 tests, 0 assertions, 2 failures", maybe if you
> look even further under the hood you could figure out how to get them to
> count. Or just choose to not care, but for me, that is a number I like to
> see :)

Yes, that's possible but it depends on which test framework you are
using. For MiniTest, for instance, it would probably be something
like:

  MiniTest::Assertions._assertions+=1
  raise MiniTest::Assertion.new(err)

Too bad there isn't some sort of core support for this kind of thing
that could be used across test frameworks.