The test runner looks for project files named the same as the directory and updates the TargetFramework element in them. This file was named differently, so it wasn't being identified by the test runner and the TFM wasn't being updated.
The result was that testing against a .NET 7 SDK would still build and run the application against .NET 6.
The test runner looks for project files named the same as the directory and updates the TargetFramework element in them. This file was named differently, so it wasn't being identified by the test runner and the TFM wasn't being updated.
The result was that testing against a .NET 7 SDK would still build and run the application against .NET 6.