In this page of JetBrains Rider options, you can adjust unit testing settings related to MSTest tests.
Enable MSTest support
By default, JetBrains Rider adds action indicators allowing you to execute MSTest tests right from the editor and automatically discovers MSTest tests in your solution. Clear this check box to disable this behavior.
Choose the IDE folder
As MSTest V1 is not distributed without Visual Studio, you have to specify the
Specify a custom test settings configuration (.testsettings file within your solution).