Hi Alkonaut, i'm dev on the Roslyn team, and i work closely with the group working on LiveUnitTesting (LUT). By default LUT just runs all your tests in realtim

Hi Alkonaut, i'm dev on the Roslyn team, and i work closely with the group working on LiveUnitTesting (LUT). By default LUT just runs all your tests in realtime, as you make edits. It smartly prioritized tests based on seeing what code was previously hit by tests. Now, that said, such an approach would definitely not scale up to projects with huge amount of tests, or tests that take hours and hours to run. As such, LUT provides ways to create 'test sets'. i.e. sets of tests scoped down to just the work you're doing. The intent is to have flexible way to create these sets and the individual sets can be set up to run automatically or manually depending on your preference. A nice things is that all of these test run outside of code VS. So the perf of the tests is far less impactful on VS than it would be otherwise. i.e. you don't have a single GC engine trying to manage all the memory for core VS as well as whatever garbage the tests are generating. With this, and with tests running at lower pri, your editing experience should not be impacted (and we take perf impact very seriously with this feature). Cheers!