Fix for ‘System.BadImageFormatException’ when running x64 based tests inside a Azure DevOps Release

This is one of those blog posts I write to remind my future self how I fixed a problem.

The Problem

I have a release that installs VSTest and runs some integration tests that target .NET 4.6 x64. All these tests worked fine in Visual Studio. However, I got the following errors for all tests when they were run in a release

2020-04-23T09:30:38.7544708Z vstest.console.exe "C:\agent\_work\r1\a\PaymentServices\drop\testartifacts\PaymentService.IntegrationTests.dll"

2020-04-23T09:30:38.7545688Z /Settings:"C:\agent\_work\_temp\uxykzf03ik2.tmp.runsettings"

2020-04-23T09:30:38.7545808Z /Logger:"trx"

2020-04-23T09:30:38.7545937Z /TestAdapterPath:"C:\agent\_work\r1\a\PaymentServices\drop\testartifacts"

2020-04-23T09:30:39.2634578Z Starting test execution, please wait...

2020-04-23T09:30:39.4783658Z A total of 1 test files matched the specified pattern.

2020-04-23T09:30:40.8660112Z   X Can_Get_MIDs [521ms]

2020-04-23T09:30:40.8684249Z   Error Message:

2020-04-23T09:30:40.8684441Z    Test method PaymentServices.IntegrationTests.ControllerMIDTests.Can_Get_MIDs threw exception:

2020-04-23T09:30:40.8684574Z System.BadImageFormatException: Could not load file or assembly 'PaymentServices, 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.

2020-04-23T09:30:40.8684766Z   Stack Trace:

2020-04-23T09:30:40.8684881Z       at PaymentServices.IntegrationTests.ControllerMIDTests.Can_Get_MIDs()

2020-04-23T09:30:40.9038788Z Results File: C:\agent\_work\_temp\TestResults\svc-devops_SVRHQAPP027_2020-04-23_10_30_40.trx

2020-04-23T09:30:40.9080344Z Total tests: 22

2020-04-23T09:30:40.9082348Z      Failed: 22

2020-04-23T09:30:40.9134858Z ##[error]Test Run Failed.

Solution

I needed to tell vstest.console.exe to run x64 as opposed to it’s default of x32. This can be done with a command line override –platform:x64

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