VSTest Build execution - is not loading dependent project assemblies - continuous-integration

Question

I have created a Service Fabric application and added an MSTest project in the solution to test methods in the services.
For that, I have added a service project reference to HelloWorldAPI.dll in the MSTest project.
After this, I created an automated build definition in Visual Studio Team Services (was VSO), and I'm trying to execute Visual Studio Test cases through this build. However, I am getting the below error:
> Starting task: Test Assemblies **\*test*.dll;-:**\obj\**
******************************************************************************
Executing the powershell script: C:\LR\MMS\Services\Mms\TaskAgentProvisioner\Tools\agents\1.104.1\tasks\VSTest\1.0.50\VSTest.ps1
Working folder: C:\a\1
Executing C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\CommonExtensions\Microsoft\TestWindow\vstest.console.exe "C:\a\1\s\POC\ServiceFabric\HelloWorld\UnitTestProject1\bin\Debug\Microsoft.VisualStudio.QualityTools.UnitTestFramework.dll" "C:\a\1\s\POC\ServiceFabric\HelloWorld\UnitTestProject1\bin\Debug\UnitTestProject1.dll" /logger:trx
Microsoft (R) Test Execution Command Line Tool Version 14.0.25420.1
Copyright (c) Microsoft Corporation. All rights reserved.
Starting test execution, please wait...
Failed GetHelloWorldString
Error Message:
Unable to create instance of class HelloWorld.Test.ProductContollerTest. Error: System.BadImageFormatException: Could not load file or assembly 'HelloWorldAPI, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. An attempt was made to load a program with an incorrect format..
Stack Trace:
at HelloWorld.Test.ProductContollerTest..ctor()
- ***Error Message:***
*
**
> Unable to create instance of class
> HelloWorld.Test.ProductContollerTest. Error:
> System.BadImageFormatException: Could not load file or assembly
> 'HelloWorldAPI, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'
> or one of its dependencies. An attempt was made to load a program with
> an incorrect format..
**
*
Please find the attached below configuration details in Team Services:
VSTest Configuration Details
Stack Trace:
at HelloWorld.Test.ProductContollerTest..ctor()
Failed GetAllProductListTest
Test Run Failed.
Results File: C:\a\1\TestResults\buildguest_TASKAGENT5-0026 2016-08-22 08_48_07.trx
Total tests: 2. Passed: 0. Failed: 2. Skipped: 0.
Test execution time: 0.4165 Seconds
System.Exception: VSTest Test Run failed with exit code: 1
Publishing Test Results...
Test results remaining: 2
Published Test Run : https://jci.visualstudio.com/Project%20-%20Microservices/_TestManagement/Runs#runId=3191&_a=runCharts
Is it possible to load dependent (project) assembly in the VSTest execution step?

Answer 1

I am too late to answer this. But today I was facing the same issue and so I thought to share my solution here. It may help someone.
Note - I am using Visual Studio 2017.
For me it was happening because of inconsistent processor architectures (32 bit / 64 bit) used across assemblies/projects.
To fix this, I set the architectures of all projects to 64 bit (x64). You can do this by right clicking your solution in Solution Explorer, then Properties > Configuration Properties and click on the Configuration Manager button.
Next I set the Default Processor Architecture of tests to x64 . You can do this by clicking on the Test menu > Test Settings > Default Processor Architecture > x64.
Make sure you are executing the library produced at the correct path - \bin\x64\Release\mytests.dll