Testhost.exe has exited with code -1 (0xffffffff)

I am attempting to override a few variables in my integration test with secrets sourced from KeyVault via a variable group within the build pipeline.

I have added a .runsettings file & I'm able to retrieve the dummy variables when I debug through the test. The test however exits abruptly as soon as the instruction to read the dummy value has been executed with the error below:

Value of CrmClientSecret is JustSomeSecret
Step into: Stepping over non-user code 
'IntegrationTests.Helpers.Helper.DeleteUserFromCRM' Step into: Stepping over 
non-user code 'IntegrationTests.Helpers.Helper. d__4..ctor' 'testhost.exe' 
(CLR v4.0.30319: TestSourceHost: Enumering source 
(C:\source\repos\Azure\Integrat ionTests\bin\Debug\Tests.dll)): Loaded 
'C:\source\repos\Azure\IntegrationTests\bin\Debug\Utilities.dll'. Symbols 
loaded. The thread 0x527c has exited with code 0 (0x0). The program '[26720] 
testhost.exe' has exited with code -1 (0xffffffff). The program '[26720] 
testhost.exe: Program Trace' has exited with code 0 (0x0).

Any help is appreciated

The solution is hosted in Visual Studio Ent 2017. The test project is net 4.61 & the following Nuget packages are installed:

1. Microsoft.NET.Test.Sdk v 15.9.0
2. MSTest.TestAdapter v 1.3.2
3. MSTest.TestFramework v 1.3.2
4. NUnit3TestAdapter version 3.11.0

Here are my test results:

<?xml version="1.0" encoding="utf-8"?>
<RunSettings>
<RunConfiguration>
<MaxCpuCount>2</MaxCpuCount>
<ResultsDirectory>.\TestResults</ResultsDirectory>
<TargetPlatform>x64</TargetPlatform>
<TargetFrameworkVersion>Framework45</TargetFrameworkVersion>
<TestAdaptersPaths>%systemdrive%\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\2017\ENTERPRISE\COMMON7\IDE\EXTENSIONS\TESTPLATFORM\Extensions</TestAdaptersPaths>
<TestSessionTimeout>10000</TestSessionTimeout>
</RunConfiguration>
<DataCollectionRunSettings>
<DataCollectors>
  <DataCollector friendlyName="Code Coverage" uri="datacollector://Microsoft/CodeCoverage/2.0" assemblyQualifiedName="Microsoft.VisualStudio.Coverage.DynamicCoverageDataCollector, Microsoft.VisualStudio.TraceCollector, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">
<Configuration>
<CodeCoverage>
<ModulePaths>
<Exclude>
<ModulePath>.*CPPUnitTestFramework.*</ModulePath>
</Exclude>
</ModulePaths>
<UseVerifiableInstrumentation>True</UseVerifiableInstrumentation>
<AllowLowIntegrityProcesses>True</AllowLowIntegrityProcesses>
<CollectFromChildProcesses>True</CollectFromChildProcesses>
<CollectAspDotNet>False</CollectAspDotNet>
</CodeCoverage>
</Configuration>
</DataCollector>
<DataCollector uri="datacollector://microsoft/VideoRecorder/1.0" assemblyQualifiedName="Microsoft.VisualStudio.TestTools.DataCollection.VideoRecorder.VideoRecorderDataCollector, Microsoft.VisualStudio.TestTools.DataCollection.VideoRecorder, Version=15.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" friendlyName="Screen and Voice Recorder">
 </DataCollector>
 </DataCollectors>
 </DataCollectionRunSettings>
 <TestRunParameters>
 <Parameter name="AmbassadorsDbConnectionString"
 value="TheConnectionString" />
<Parameter name="CRMClientSecret" value="JustSomeSecret" />
<Parameter name="webAppPassword" value="Password" />    
</TestRunParameters>
<MSTest>
  <MapInconclusiveToFailed>True</MapInconclusiveToFailed>
  <CaptureTraceOutput>false</CaptureTraceOutput>  
  <DeleteDeploymentDirectoryAfterTestRunIsComplete>False
<DeploymentEnabled>False</DeploymentEnabled>
<AssemblyResolution>
  <Directory path="D:\myfolder\bin\" includeSubDirectories="false"/>
</AssemblyResolution>
</MSTest>
</RunSettings>

You can use the blame option to collect the dump and analyze the cause for the crash

https://github.com/Microsoft/vstest-docs/blob/master/RFCs/0024-Blame-Collector-Options.md