Tests: Don't depend on tester's system timezone for success

[kisaragi-hiu]

• Org timestamps use tester's timezone, so the ideal value should too
• ts-format accepts "%z" just like format-time-string, so it's reasonable to expect it to support timezones. Add that into its ideal value.

This should fix #6.

This will make ts-format in its current form fail its test—I think that's justified, as it currently throws away the timestamp's timezone information and inserts the local timezone into its output.

[alphapapa]

Thanks.

This will make ts-format in its current form fail its test

Do you mean that this branch fixes one test and breaks another?

[kisaragi-hiu]

I mean that it fixes the test, which exposes the fact that ts-format throws away timezones, which makes the test not pass (when system timezone don't happen to line up).

[Levenson]

@alphapapa Can we merge this and #9? Currently emacs-ts build is broken on Guix, because of the #9.

Tests do not work if you are on a different timezone anyway, so we won't break anything. WDYT?

[alphapapa]

Sorry for the delay. See commits linked on #18.

In this PR, adding :tz-offset to the ts-format test in the make-ts call is fine, but changing the other tests to pass seems to paper over the underlying problem, which is that formatting timestamps needs to take the time zone into account and allow it to be specified. I'd rather fix that properly.

[alphapapa]

Quoting myself:

In this PR, adding :tz-offset to the ts-format test in the make-ts call is fine

Actually, that doesn't seem to work properly, because the :tz-offset specified in make-ts doesn't affect the resulting timestamp and formatted string. ts-format needs to handle this directly. And the fact that specifying the offset in make-ts doesn't have any effect needs to be documented.