Support generating MailAddress instances

It would be great if FsCheck would be able to generate MailAddress instances. I could work on this, but first I’d like to know if this is something that you’d support.

[kurtschelfthout]

That’s probably because we only target net standard 1.6 now, which doesn’t have MailAddress. I’m planning to target 2.0 specifically as per nuget recommendations in the next minor release, which should solve that (if MailAddress is in the 2.0 API surface, that is).

[ploeh]

As a an experienced programmer, I’d like a MailAddress generator to seek out as many exotic values as possible. You may want to consider the following, however:

If the target is to generate MailAddress values, you may need to constrain the generated values to those that MailAddress considers valid. It wouldn’t surprise me if there are strings that are considered valid according to whatever specification defines SMTP addresses, but that MailAddress doesn’t accept.

On the other hand, if that’s the case, then .NET is open source too, as well 😉

The other issue worth considering is that some generated email addresses may represent real addresses.

When FsCheck is used against pure functions, that isn’t an issue, but if someone ever decides to use FsCheck for integration testing, a side effect could be that email are sent to real mail boxes.

If that ever happens, if someone wants to place the blame, the only reasonable target for the blame ought to be the developer who chose to use FsCheck against code that sends email. Still, some people aren’t reasonable, particularly when their ass is on the line, so we could hypothetically risk that someone tries to blame FsCheck.

I still think we should generate addresses according to all sorts of edge cases, but I think at least we should put a warning in the documentation to the effect that it may generate real addresses, and that it’s the users’ responsibility if emails are sent to real mail boxes as a result of running tests.