Testcases for NSDateFormatter


A few weeks ago I opened [SR-208] Setting .dateFormat of NSDateFormatter has no effect · Issue #4375 · apple/swift-corelibs-foundation · GitHub as it appears
setting the dateFormat property of NSDateFormatter has no effect. It's
been open for a while and I thought I'd start looking at whether or not I
could help, and decided to first start with getting NSDateFormatter
included in TestFoundation.

Before moving on further and issuing a PR, I would appreciate feedback on
the approach that I'm taking here:


The first tests are only looking at the dateStyle property, and I've
included tests for the various styles as they are rendered for the en_US
locale. The intent is to add support for validating additional locales in
the future.

Since strptime doesn't appear to be available to the Glibc module I'm using
a quick Python script included in Resources/ to take a format string and
render a human-friendly date.

At the moment I know there is a discrepancy between what NSDateFormatter
and the python driver can emit, the python script is currently adjusting to
my timezone and not using UTC, but that will be fixed before a PR is
issued. I'll also add the timeStyle property and then continue to add

Thoughts and comments most welcome, and Happy New Year.