NCrunch is an automated concurrent testing tool for Visual Studio .NET.
It intelligently runs automated tests so that you don't have to, and gives you a huge amount of useful information about your tested code, such as code coverage and performance metrics, inline in your ID.
.NET code coverage analysis tool. Supports MSTest, NUnit, xUnit, and MSpec. Integrates with Visual Studio and ReSharper
dotCover vs OpenCover opinions
Sadly OpenCover still doesn't support .netcore or standard projects. DotCover does it well.