binary: Add error handling

[kytrinyx]

This adds some additional test cases to clarify the behavior around
the conversion of valid/invalid binary input.

See exercism/problem-specifications#95

[kotp]

The example does not adhere to the "do the conversion yourself" but it is a sanity check that everything is working as it should be... trusting the implementers of the language more than a 'self made' solution. The educational value is not in the example.rb file itself, so I think this is OK to do.

[kytrinyx]

The example does not adhere to the "do the conversion yourself" but it is a sanity check that everything is working as it should be... trusting the implementers of the language more than a 'self made' solution.

I'm not sure what you mean. The example does the conversion manually.

[kotp]

Yes, but it uses a built in method that does this conveniently, rather than writing the implementation explicitly. Using to_s(base) is probably not really the goal, based on the README. But it is definitely good as the definitive example that is expected in the way that it is to work.

[kotp]

Specifically, my changes to example.rb as:

  def to_decimal
    digits.to_i(2)
  end

[kytrinyx]

The point is to not use to_s(base), though.

[kytrinyx]

Oh, I didn't see your changes. That makes sense. I don't want to use digits.to_i(2) since the whole point of the exercise is to understand binary conversion enough to do it manually.

[kotp]

Yes, but the nitpickers don't see the example, right? It is a different view point?

[kotp]

if I do the 'thing to measure against' in the tests, then it sort of exposes this. If I leave it in the more 'hidden' example.rb file, then it does what is intended, cleanly.

[kytrinyx]

Right now the example solution is only used to test the test suite. I guess that means that it's OK to use a solution that would be discouraged on the site, but it seems wrong to me in a way that I'm unable to articulate.

[kotp]

I have the same little nag as well. I think it is because of the conflicting point of view. It does avoid bugs that a 'homegrown' solution could potentially introduce though.

[kytrinyx]

I see how it could avoid the bugs that a homegrown solution might have, but this is really a trivial problem, and the homegrown solution shouldn't have bugs.

[kotp]

Then just the style changes then...

[kytrinyx]

Okay :)