Error Running WebTest; Build Error = The "EntityDeploy" task could not be loaded from the assembly

Today I saw an error message trying to run a web test. I added some validation rules to a web test then tried running it. Also hovered over the Server Explorer tab at the same time.

I have reproduced this error; it happens if you click Run Test while hovering over Server Explorer at the same time. The error persists until you expand Server Explorer.

Error message:
The test could not be run because of the following exception: Assembly is still being loaded. (Exception from HRESULT: 0x80131016)

Build Error:
The "EntityDeploy" task could not be loaded from the assembly C:\WINDOWS\Microsoft.NET\Framework\v3.5\Microsoft.Data.Entity.Build.Tasks.dll. Assembly is still being loaded. (Exception from HRESULT: 0x80131016) Confirm that the ,UsingTask> declaration is correct, and that the assembly and all of its dependencies are ready