How to configure Test Runner Environment Variables for Unit Test projct in JetBrains Rider

Problem

Cannot override environment variables for specific Unit tests project using standard configuration methods in JetBrains Rider's test runner. The Environment Settings section in the Test Runner settings allows to override/add environment variables per solution. One might want to have specific environment variables per exact project (.csproj)

Resolution

To set environment variables for a specific test project, follow these steps:

1. Use a .runsettings File: Create a SampleFileName.runsettings file within the same directory as your C# project file (.csproj).

2. Add Configuration to the Project File: Integrate the path to the .runsettings file in your project's C# project file by adding the following property:

   <PropertyGroup>
       <RunSettingsFilePath>$(MSBuildProjectDirectory)\SampleFileName.runsettings</RunSettingsFilePath>
   </PropertyGroup>
   

3. Define Environment Variables in .runsettings: Populate the .runsettings file with the desired environment variable values in the following format:

   <?xml version="1.0" encoding="utf-8" ?>
   <RunSettings>
     <RunConfiguration>
       <EnvironmentVariables>
         <VariableName1>Value1</VariableName1>
         <VariableName2>Value2</VariableName2>
       </EnvironmentVariables>
     </RunConfiguration>
   </RunSettings>
   

4. Verify Settings in JetBrains Rider: Launch your test project and confirm that the test runner adheres to the defined environment variables.