Recently I came to know about the nuget based adapter/runner (http://xunit.github.io/docs/running-tests-in-vs.html)
I was trying to understand how these runners/adapters are recognized by Visual Studio and then used by the TestWindow.
For example, if I install "xunit.runner.visualstudio" nuget package all the xUnit based tests in my project are discovered and displayed in the Test Window.
I am trying to understand how does VS hook the Test Discovery using the package installed in packages folder?
Where/how do VS and nuget based adapter get hooked?
I tried finding this information but my google fu failed me. :(
I checked answer for the question (Custom test adapter installed via NuGet isn't discovering tests) and it does say that VS copies the packages to the path %TEMP%\VisualStudioTestExplorerExtensions but that's pretty much it.
Since this involves a lot of how VS works internally, I don't think you'll get a totally definitive answer. However, to solve the issue you linked to I looked at a bunch of disassembled code, so I have a pretty good idea. Here's how it seems to work:
- You build a project that references a package named Sample.TestAdapter
- VS copies Sample.TestAdapter directory from packages to %TEMP%\VisualStudioTestExplorerExtensions
- Something triggers test discovery - rebuild always does, sometimes incremental builds do too. vstest.console.exe is useful here for debugging.
- VS launches vstest.discovery.exe which looks in VisualStudioTestExplorerExtensions for an assembly that implements ITestDiscoverer
- If an ITestDiscoverer is found, VS calls it with a list of assemblies that may contain tests
- Tests that are discovered are sent back to VS by your test adapter
So, as far as I can tell it's a pretty simple reflection based plug-in architecture. Hope that helps.
