Integration tests for date parsing

[Maximkaaa]

There are a lot of open issues both here and in the coreutils repo related to invalid parsing of dates. Some of them are already fixed, but not closed, some are still pending, some have open PRs, some are related and report the same thing. And some issues are not discovered yet.

So I thought it would be nice to have an easy to navigate list of things that work and do not work, and an easy way to check and update it. So I came up with this.

The tests in this PR basically cover everything (and a little more) covered by https://www.gnu.org/software/coreutils/manual/html_node/Calendar-date-items.html (not entirely true, they cover only what should work, but do not test things that shouldn't work).

Before I go on to other chapters of that manual, I would like to know what the maintainers think about it:

• how do you feel about the format of the tests?
• how do you feel about adding dev dependency to rstest?
• do you think it's better to create one huge PR with all integration tests at once, or add them bit my bit in separate PRs (for example, by chapter in the manual)?

[Maximkaaa]

@sylvestre @cakebaker A polite ping. If this is not something that is needed for parse_datetime, let's close this PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 0.00%. Comparing base (30cb26d) to head (7260b0a).
Report is 5 commits behind head on main.

Additional details and impacted files

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[sylvestre]

Thanks

[cakebaker]

Hm, at least on my machine all new tests fail with:

thread 'test_absolute_date_numeric::case_01_iso8601' panicked at tests/common/mod.rs:10:5:
assertion `left == right` failed: Input value: 2022-11-14
  left: "2022-11-14 00:00:00+02:00"
 right: "2022-11-14 00:00:00+00:00"

It looks like it's because I'm currently in UTC+2 and the tests expect UTC.

Edit: I fixed it in #162