NETStandard 1.3 support dropped in NUnit 3.10

[jrjrguo]

Hello,
The support for .NET Standard 1.3 seems to be dropped in NUnit 3.10, and now the lowest .NET Standard is 1.6, which does not work with Universal when targeting RS1 or RS2 (the latest version that works is 1.4). I might have missed it, but I did not find any notes on why .NET Standard 1.3 support is dropped. So, just wondering what options there might be to for RS1/RS2? Could we bring back earlier .NET Standard support?

[mikkelbu]

Hi @jrjrguo
There was a lot of discussion of this in #2380. Below I've found some of the comments mentioning 1.3 (especially the later ones are relevant). That being said, I'm no expert in .NET Standard, so for answering your question, I think we will have to wait for either @jnm2 or @rprouse.

#2380 (comment)
#2380 (comment)
#2380 (comment)
#2380 (comment)
#2380 (comment)
#2380 (comment)

[jnm2]

Wow Mikkel! Thanks for the quick links!

@jrjrguo netstandard1.3 presented a significant amount of work and the only platform loss was dropping UWP 10 in favor of UWP 10.0.16299. I believe we'd all like to support any platform on which people are actually running their tests.

What is your test project's target framework, uwp10.0?
If so, then we'd most likely be deciding whether we want to add (and specially test) a uwp10.0 build or a netstandard1.4 build.

[rprouse]

Part of the decision to drop 1.3 was we only had very rudimentary support for running UWP 10 tests and nobody was using that runner. You had to compile a Xamarin.Forms test app running UWP and manually run the tests.

@jrjrguo are you upgrading an existing project? If so, what were you using to run your UWP tests?

[jrjrguo]

Thanks for all the replies!
@jnm2 Yes, we are targeting uwp10.0 and we need to keep supporting it.
@rprouse We are not using nunit.xamarin to run UWP tests currently. We have our own uwp test runner that is still depending on NUnit 3.6.1, but we do want to switch to nunit.xamarin for all platforms.

[steffenloesch]

uap10.0 is still very relevant, because it's the only way to build a universal app that runs on Windows 10 that is older than the Windows 10 Fall Creators Update from October 2017. The thing is that the Windows that is installed on Microsoft Surface Hubs is based on the Windows 10 Creators Update from April 2017, and that is not going to change quickly. So if you want to build Universal Apps in C# that run on Surface Hubs, then you have to use uap10.0 for the foreseeable future.

This is the case for us. I'm working at Microsoft in a team with @jrjrguo, we're around 80 developers and we have to target uap10.0 We're using NUnit to run tests on uap10.0 , using a in-house test runner. We'd love to keep using an up-to-date NUnit (and possibly switch to the NUnit.Xamarin runner).
For that, how much effort would it be possible to bring the netstandard1.4/netstandard1.3 build back?

[jnm2]

I'm looking at it now. netstandard1.4 is much less complex to build for than uap10.0, especially considering that we compile cross-platform. Depending what the difference to NUnit is between 1.4 and 1.6, we might not keep both.

[jnm2]

The differences between .NET Standard1.4 and 1.6 can be easily bridged with reflection. @rprouse, what do you think? If we do 1.4 in place of 1.6, we won't have to figure out how to do a proper csproj test matrix. 😇

[jnm2]

https://github.com/nunit/nunit/compare/jnm2/netstandard1.4

First commit adds netstandard1.4 support and builds successfully.
Second commit removes netstandard1.6 and builds successfully.
Tests don't run yet, was a little surprised to see this:

System.Reflection.TypeExtensions is not supported on NET Standard 1.3 or 1.5.

Looks like it means I'll have to put NUnit.Compatibility back...

[steffenloesch]

Wow, I did not expect such quick actions. Thanks for looking into it @jnm2!

[jnm2]

It seems like some sort of shortcut has been taken in System.Reflection.TypeExtensions 4.5. Had a moment of inspiration and tried 4.4 which resulted in all tests running and passing on the first shot. 🎉

#2894

[jnm2]

The netstandard1.4 nupkg is building fine in my ad-hoc uap10.0 and netcoreapp1.1 test projects.

It seems like this will be a viable way of running acceptance tests on the nupkg itself as a build step after package: https://github.com/nunit/nunit/tree/jnm2/nupkg_tests/tests

I just need more time to learn how to drive UWP tests from the command line.

[ChrisMaddock]

It seems like some sort of shortcut has been taken in System.Reflection.TypeExtensions 4.5. Had a moment of inspiration and tried 4.4 which resulted in all tests running and passing on the first shot. 🎉

Are you referring to the _._ files in the NuGet package here?

I had lots of fun with these in #2237. My understanding is that that file is put in place when the platform doesn't support the .NET Standard API yet - so that the package fails to restore for the platform at restore time, as opposed to throwing errors at runtime.

If that's correct, and the _._ file has been added between 4.4 and 4.5, then I'm not sure reverting to the older package version is necessarily the best solution. It looks like the placeholder was explicitly added in here - but without much background info...maybe some of the UWP bods here may know more?

To clarify - my concern is that depending on v4.4 of the package may allow us to build, but instead expose us to runtime errors. If that's the case - then adding back our own Reflection functionality seems preferable. If I've misunderstood how all this works, then taking on the package dependency seems ideal. 😄