Conversion from TestCase string parameter to DateTimeOffset

[Thorarin]

TestCaseAttribute includes behavior to perform conversion of some parameter types to the desired target type. Amongst others, conversion from String to DateTime and from String to TimeSpan are supported. This is useful, because no constants of these target types can be defined in the TestCaseAttribute.

It would be nice if DateTimeOffset could be added could be added to the list of supported conversions.

For example:

[TestCase("2018-10-09 15:15:00+02:00")]
public void MyTest(DateTimeOffset foo)
{
}

Convert.ChangeType does not appear to work for DateTimeOffset, so the code would be similar to the code for TimeSpan.

I wouldn't mind creating a PR for this if that helps; it seems fairly straightforward to add.

NUnit version: latest master

[jnm2]

I like this. If I understand correctly, Convert was a legacy class to help folks migrate to .NET from older VB. Type converters were the modern (.NET Framework 1.0) answer. If we simply get the default type converter for the parameter type and attempted to convert the string that way, would it behave the way you'd like?

@nunit/framework-team What do you think about TypeConverter? Needs https://www.nuget.org/packages/System.ComponentModel.TypeConverter/ for the .NET Standard 1.4 build, and the .NET team really intends us to use packages like that and report issues if any still exist.

[oznetmaster]

Convert is used for anything that implements the IConvertible interface.

TypeConverter is for anything else.

I think we should fully support both.

[jnm2]

Good. Yes, I'm not proposing to stop using Convert. That would almost surely break someone.

[stevenaw]

@Thorarin Were you still working on this, or do you mind if give it a try?

[jnm2]

@stevenaw I do believe this item is free to work on, since we haven't put it up for grabs yet. All the feedback so far is positive, so let's go ahead.

@rprouse Does it seem fair to go ahead and assign @stevenaw?