leap: Make the test descriptions consistent

[guntbert]

description adheres to the schema: leap year / standard year, then either the century or the year number itself.

No testcases have been altered/added/removed.

Related: exercism/discussions#104

[Insti]

@guntbert please read this comment about test descriptions.

The descriptions you have here are OK, but they don't really describe WHY those particular years are good numbers to test.

What:

      {
          "description": "leap year in twentieth century",
          "input": 1996,
          "expected": true
       },

Why:

      {
          "description": "a leap year is evenly divisible by 4",
          "input": 1996,
          "expected": true
       },

[guntbert]

@Insti I agree that we should describe the why instead of the what. But I have my doubts about your proposal. Case in question:

"description": "leap year in twentieth century",

says

"1996 is chosen as an arbitrary leap year from the twentieth century"

whereas

"description": "a leap year is evenly divisible by 4",

merely restates the facts given in description.md

I think most of the test cases should be reevaluated, asking if they contribute anything useful - but I did not want (as a newcomer) to overthrow the complete test suite and thus just changed the descriptions.

If you think this should be done right now I'll do it :-)

[Insti]

I did not want (as a newcomer) to overthrow the complete test suite and thus just changed the descriptions.

That is certainly a good approach. 👍

I think most of the test cases should be reevaluated, asking if they contribute anything useful ...
... If you think this should be done right now I'll do it :-)

That would be good.

[Insti]

I agree that we should describe the why instead of the what. But I have my doubts about your proposal. Case in question:
"description": "leap year in twentieth century",
says
"1996 is chosen as an arbitrary leap year from the twentieth century"
whereas
"description": "a leap year is evenly divisible by 4",
merely restates the facts given in description.md

This, to me, is a feature. The rules should be encoded in and described by the tests, description.md provides 'color' and allows a written introduction/specification of the problem.

"description": "leap year in twentieth century",
says
"1996 is chosen as an arbitrary leap year from the twentieth century"

Why is it relevant that it is in the twentieth century?
How do we know it is a leap year?

How about this made up (counter) example:

{
   "description": "floopy year in twentieth century",
   "input": 1969,
   "expected": true
},

What does this tell you about floopy years?

(Sorry about the mangled quote formatting at the top.)

[Insti]

@guntbert did you want to continue this PR for the updated tests or shall we merge this one and you can make a new one for the updated tests?

[guntbert]

@Insti as I am a bit pressed for time right now (several tests to grade :-)) I'd rather take a fresh approach with a new PR. Fine if you merge this one but I agree that it is suboptimal.

[Insti]

It might not be perfect yet, but it is an improvement.

Thanks for your contribution @guntbert. ❤️