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MSTest 2.2.4 does not work with [DataTestMethod] [DynamicData] and a complex object

See original GitHub issue

Description

Everything was working fine in 2.2.3. Then we updated to 2.2.4 and it does not work anymore. So we have some classes with [DataTestMethod] and some dynamic data that we feed into it. The tests were green in 2.2.3 and upgrading to 2.2.4 break them with this error:

C:\Users\mme\Documents\GitHub\MsTest224DataTestBug\MsTest224DataTestBug>dotnet test MsTest224DataTestBug.csproj
 Determining projects to restore...
 Restored C:\Users\mme\Documents\GitHub\MsTest224DataTestBug\MsTest224DataTestBug\MsTest224DataTestBug.csproj (in 529 ms).
 MsTest224DataTestBug -> C:\Users\mme\Documents\GitHub\MsTest224DataTestBug\MsTest224DataTestBug\bin\Debug\net5.0\MsTest224DataTestBug.dll
Test run for C:\Users\mme\Documents\GitHub\MsTest224DataTestBug\MsTest224DataTestBug\bin\Debug\net5.0\MsTest224DataTestBug.dll (.NETCoreApp,Version=v5.0)
Microsoft (R) Test Execution Command Line Tool Version 16.10.0
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.
An exception occurred while invoking executor 'executor://mstestadapter/v2': Type 'MsTest224DataTestBug.MyStringContainer' with data contract name 'MyStringContainer:http://schemas.datacontract.org/2004/07/MsTest224DataTestBug' is not expected. Add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.
Stack trace:
  at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeAndVerifyType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, Boolean verifyKnownType, RuntimeTypeHandle declaredTypeHandle, Type declaredType)
  at System.Runtime.Serialization.Json.XmlObjectSerializerWriteContextComplexJson.SerializeWithXsiTypeAtTopLevel(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle originalDeclaredTypeHandle, Type graphType)
  at System.Runtime.Serialization.Json.DataContractJsonSerializerImpl.InternalWriteObjectContent(XmlWriterDelegator writer, Object graph)
  at System.Runtime.Serialization.Json.DataContractJsonSerializerImpl.InternalWriteObject(XmlWriterDelegator writer, Object graph)
  at System.Runtime.Serialization.XmlObjectSerializer.InternalWriteObject(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
  at System.Runtime.Serialization.XmlObjectSerializer.WriteObjectHandleExceptions(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
  at System.Runtime.Serialization.Json.DataContractJsonSerializerImpl.WriteObject(XmlDictionaryWriter writer, Object graph)
  at System.Runtime.Serialization.Json.DataContractJsonSerializerImpl.WriteObject(Stream stream, Object graph)
  at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Helpers.DataSerializationHelper.Serialize(Object[] data)
  at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.ObjectModel.UnitTestElement.ToTestCase()
  at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.UnitTestDiscoverer.SendTestCases(String source, IEnumerable`1 testElements, ITestCaseDiscoverySink discoverySink, IDiscoveryContext discoveryContext, IMessageLogger logger)
  at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.UnitTestDiscoverer.DiscoverTestsInSource(String source, IMessageLogger logger, ITestCaseDiscoverySink discoverySink, IDiscoveryContext discoveryContext)
  at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestExecutionManager.RunTests(IEnumerable`1 sources, IRunContext runContext, IFrameworkHandle frameworkHandle, TestRunCancellationToken cancellationToken)
  at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.MSTestExecutor.RunTests(IEnumerable`1 sources, IRunContext runContext, IFrameworkHandle frameworkHandle)
  at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.RunTestsWithSources.InvokeExecutor(LazyExtension`2 executor, Tuple`2 executorUriExtensionTuple, RunContext runContext, IFrameworkHandle frameworkHandle)
  at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.BaseRunTests.RunTestInternalWithExecutors(IEnumerable`1 executorUriExtensionMap, Int64 totalTests)


Additionally, path to test adapters can be specified using /TestAdapterPath command. Example  /TestAdapterPath:<pathToCustomAdapters>.

Steps to reproduce

Here is a full sample reproducing the bug: https://github.com/TheFireCookie/MsTest224DataTestBug In this repo, there is a folder MsTest223DataTestBug in which the command ‘dotnet test’ works correctly, the other folder is MsTest224DataTestBug and in this one, it’s exactly the same code except I’ve upgraded MSTest to 2.2.4 and there a ‘dotnet test’ fails with the error written earlier.