Transpose: add test-case

[pheanex]

The current version of the transpose-test cases (1.0.0) seem to miss out on a case:
There are two test-cases which cover the correct right-stripping of white-space
("first line longer than second line" and "many lines"), yet they do not cover the case, where you have to right-trim whitespace with multiple lines at the end (Idk if i describe it correctly).
I noticed it, when I checked some implementations in the Python track which failed my following suggested test:

{
  "description": "descending line length",
  "property": "transpose",
  "input": [
    "The longest line.",
    "A longer line.",
    "A long line."
  ],
  "expected": [
    "TAA",
    "h  ",
    "ell",
    " oo",
    "lnn",
    "ogg",
    "ne ",
    "grl",
    "e i",
    "sln",
    "tie",
    " n.",
    "le",
    "i.",
    "n",
    "e",
    "."
  ]
}

[rpottsoh]

https://github.com/exercism/problem-specifications/blob/master/exercises/transpose/description.md

[rpottsoh]

Interesting. I am not seeing how the new test is different from the two cases you mentioned. Is it the fact that you are proposing three lines instead of two? Why doesn't "many lines" cover this?

I have not attempted this exercise, so I have no familiarity with it other than the documentation and test data.

[pheanex]

The difference is, that this test is the only one that checks if the right-side-space-trimming works on more than just the last line in "expected". "Many lines" does not cover this, since the last line of input is too long (you can see that only the last line in "expected" needs to get right-trimmed)

[pheanex]

I just came up with an even better test-case for this:

{
  "description": "mixed line length",
  "property": "transpose",
  "input": [
    "The longest line.",
    "A long line.",
    "A longer line.",
    "A line."
  ],
  "expected": [
    "TAAA",
    "h   ",
    "elll",
    " ooi",
    "lnnn",
    "ogge",
    "n e.",
    "glr",
    "ei ",
    "snl",
    "tei",
    " .n",
    "l e",
    "i .",
    "n",
    "e",
    "."
  ]
}

Maybe @ErikSchierboom or @rbasso want to review this?

[ErikSchierboom]

I think this is a very nice addition. It may even be a replacement for the existing "many lines" case, as this case handles the same problem but in a better, more interesting way.