DnD Character - confused about the purpose and execution of the exercise about typescript

[ireddick]

After some thought:

1. I'll create a PR to initially ignore all but the first test

2. Having looked at the test names and test order in the canonical data for the exercise here:

https://github.com/exercism/problem-specifications/blob/main/exercises/dnd-character/canonical-data.json

I see that the test order, test names, and the test with description 'each ability is only calculated once' (which tests nothing as far as I can make out) are all reflected in the tests on this track, so I'd be hesitant creating a PR to change any of these locally (I'm not sure how in-sync these things have to be).

I think at this point I'm going to say that I simply don't like this particular exercise and move on.

[SleeplessByte]

I think these are very good questions, but the answers aren't exceptionally straight-forward. Here are a few comments based on your issue, but this is not a full-fledged response to the entire thing as a whole (as I'm a bit time constrained right now -- but I did want to give you some response soon).

1. As you mentioned, the common canonical problem specification gives a bit of insight on what is possible and what's not possible. If the abstract phrasing there is applied to TypeScript, it's basically saying:
   • It is impossible to test for randomness. You can only make a test that attempts to find within some reasonable probability that something is truly random. For example, a test with checks that asserts if the first 10 dice rolls are not all 6 are, however improbable, not actually testing that it's random. Getting 10 rolls of 6, assuming true randomness, is about 1.65e-8 which is small, but definitely in the space of possibility. Making the number larger makes it less probably that this test fails when something is truly random, but it doesn't test for it.
   • It is possible to test the usage of the randomizer (in other words: is the randomizer being called when you expect it).
   • It is possible to invert the tests making it more and more probable that something is implemented correctly.
   • The whole thing about property based testing is more a note for implementers and not for students, and it's there because it attempts to explain how maintainers could implement this test suite in their track.
2. From the original issue: exercism/problem-specifications#616 and the original PR exercism/problem-specifications#1397 we can find some of the discussion of what you mention. Basically it was determined that we (at this point) do not at randomness tests but usage of randomness (for example: exercism/problem-specifications#1397 (comment))
3. This then means that most tests get a "best effort" approach (aka: exercism/problem-specifications#1397 (comment)).
4. The .prop === .prop tests try to guard for get prop() { return somethingRandom() }, which is much more common in some other languages, but that's why it is as it is.

A few thoughts based on your observations:

1. The order of the tests is sub-optimal. I will take a PR to make this better. Go for it if you feel like doing that, or we can leave this issue open is necessary.
2. The fact that none of the tests is ignored/skipped is a bug. This should be fixed. Go for it if you feel like doing that.
3. I think what may be good is mocking Math.rand() as we want people to use that anyway -- but Crypto.getRandomValues() technically could be used too. This would be additional tests, which I think would be a good idea here.
4. I don't understand your comment about "this exercise comes after Space Age". Can you elaborate on this, so I can help figuring out how we may solve this?

[ireddick]

Thanks for the in-depth response - I'll read the original idea for the exercise you linked to for more context 👍

Regarding "this exercise comes after Space Age", I was referring to the order of the exercises I encountered on this track, which I had assumed was always the same. Is that the case, or is it different each time?

[SleeplessByte]

Thanks @ireddick for your issue and PR!