If 'Unit Test Sessions' window is always opened on Visual Studio start and you'd like it not to happen, please uncheck the 'Save and restore Unit Test Sessions' checkbox located in the "ReSharper | Options | Tools | Unit Testing" dialog:

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Thank you and sorry for inconvenience!
If 'Unit Test Sessions' window is always opened on Visual Studio start and you'd like it not to happen, please uncheck the 'Save and restore Unit Test Sessions' checkbox located in the "ReSharper | Options | Tools | Unit Testing" dialog:

Very helpful! If you've ever accidentally run a test through ReSharper, it will remember... forever. This fixes the problem wonderfully!