VSTest does not run tests in X64 when specified in Platform.

I get the following error in VSO when trying to run tests in an x64 assembly.

Test run will use DLL(s) built for framework Framework45 and platform X86. Following DLL(s) will not be part of run: 

My.Tests.dll, My.Tests.dll are built for Framework Framework45 and Platform X64.

##[error]Error: None of the provided test containers match the Platform Architecture and .Net Framework settings for the test run. Platform: X86  .Net Framework: Framework45. Go to http://go.microsoft.com/fwlink/?LinkID=330428 for more details on managing these settings.

##[error]

##[error]VSTest Test Run failed with exit code: 1

In VSTest.ps1 when Invoke-VsTest is called, the variable $platform is not even passed to the cmdlet.

Invoke-VSTest -TestAssemblies $testAssemblyFiles -VSTestVersion $vsTestVersion -TestFiltercriteria $testFiltercriteria -RunSettingsFile $runSettingsFileWithParallel -PathtoCustomTestAdapters $pathtoCustomTestAdapters -CodeCoverageEnabled $codeCoverage -OverrideTestrunParameters $overrideTestrunParameters -OtherConsoleOptions $otherConsoleOptions -WorkingFolder $workingDirectory -TestResultsFolder $testResultsDirectory -SourcesDirectory $sourcesDirectory

[jemiller0]

I just upgraded to VS 2017 15.5 and now I’m getting the error. It was working fine before the upgrade. Whatever “improvements” were made to testing in 15.5 seem to have broken it for me.

[aligneddev]

I’m getting this error from VS 2017 v15.4.3.

From the runsettings documentation example “you can also change it from menu Test, Test Settings, Default Processor Architecture”.

Maybe that will help someone.