A tool similar to what you want. It generates input/output pairs from the code, aiming to maximize coverage, and allows you to convert them to unit tests with one click.

https://docs.microsoft.com/en-us/visualstudio/test/generate-...

Also known as its legacy / research project name, "Pex". The underlying algorithm technique is called "dynamic symbolic execution".

There was also similar tool for Java called "Agitar Agitator".