AssemblyInitialize/AssemblyCleanup in base class ignored in case of usage of it as base in tests from another assembly

Description

Hi guys, I have been facing the behaviour of AssemblyInitialize/AssemblyCleanup logic where they are not executed if you have a TestClass, which is a child of some base class defined in another assembly. From some point of view, this seems partially reasonable. I slightly went through your code and found, that scanning of test classes is based on AssemblyEnumerator and deciding whether a test assembly has some AssemblyInitialize or not is based on that fact. And for sure, in case of another assembly, it decides that, well, the assembly has no appropriate signatures since test classes are defined within such assembly have no direct implementation of AssemblyInitialize/AssemblyCleanup and ignore the fact that such method can be defined in a base class of test classes.

From another point of view, this seems slightly bad, since I am almost sure that most developers/teams/companies have their own infrastructure for tests where they are storing some useful cross-cutting logic, and since such infrastructure is generic, they, for sure, implement the logic for AssemblyInitialize and other lifecycle-based methods. And, for sure, a good idea for such guys is to dedicate their test infrastructure in a separate assembly, in order to reuse such logic across different projects/test-assemblies. But because of the limitations that I described above, unfortunately, it is not possible to do (without dirty workarounds).

Steps to reproduce

Create a library and add the next class that will be base for other tests:

[TestClass]
 public class TestBase 
 {
     public static StringBuilder result;
     public static readonly string resultPath = Path.Combine(Environment.CurrentDirectory, "result.txt");

     [AssemblyInitialize]
     public static void AssemblyIntialize(TestContext testContext)
     {
         File.Delete(resultPath);

         result = new StringBuilder();
         result.AppendLine(nameof(AssemblyIntialize));
     }

     [AssemblyCleanup]
     public static void AssemblyCleanup()
     {
         result.AppendLine(nameof(AssemblyCleanup));

         File.AppendAllText(resultPath, result.ToString());
     }

     [TestMethod]
     public void Test()
     {
         result.AppendLine(nameof(Test));
     }
 }

Create a unit-test project and add the next test class

 [TestClass]
    public class UnitTest1 : TestBase
    {
        [TestMethod]
        public void TestMethod1()
        {
            result?.AppendLine(nameof(TestMethod1));
        }
    }

Run TestMethod1.

Expected behavior

AssemblyIntialize
Test
AssemblyCleanup

Actual behaviour

Nothing, since the file will not be created, since AssemblyIntialize and AssemblyCleanup will not be executed.

Environment

Described logic is independent of env.

What I propose.

I understand that adding such behaviour is a breaking change. So, firstly I want to be able to make this optional when by default we preserve behaviour which is the current one. In order to propagate option I propose to add a constructor to AssemblyInitialize/AssemblyCleanup attributes with optional arg like AssemblyInitialize(AssemblyScope scope = AssemblyScope.OnlyCurrentAssembly), where AssemblyScope is an enum with a possible value like AssemblyScope.AnyAssembly. Then, in TypeCache.GetAssemblyInfo slightly change the logic in a next way: analyze declared types as before and if AssemblyInitialize/AssemblyCleanup was found, then ok, just do everything as before (because, for sure, AssemblyInitialize defined in a current assembly has more priority than inherited one). But besides analyzing declared types (if the scope was AssemblyScope.AnyAssembly) we need to analyze the first level of inheriting graph of every test and if the base class exists add it to HashSet. As soon as HashSet will be filled and if AssemblyInitialize is still not found, do the previous step recursively until the first occurrence of AssemblyInitialize or empty HashSet.

Contribution

If this seems reasonable to your team, I can make such changes by myself and cover them with tests and make a pull request.

Additional resources

• The same problem described in StackOverflow

Thanks for your attention and your work on MsTest v2

[ChristopherHaws]

your project marked with assembly initialize attribute that would simply call the assembly initialize from the other assembly you reference. This is obviously only to provide a temporary workaround for you.

This is what we are doing currently 😃

[ChristopherHaws]

What if you had to specify the class at an assembly level to ensure that the discovery process can stay fast? I could really use this feature ^_^

Something like:

[assembly: AssemblyTestClass(typeof(TestBase))]