Currently, our test util functions do not directly support working with untitled documents, as they only accept path instead of uri. Should we generalize the respond_* functions so that they could also work with uri, or we directly use respond() in the tests for untitled documents which is only a tiny portion of the test cases, maybe not worth making any changes to specific respond_* functions.

I think it should not be too difficult to support it. By the way, what will be the uri for untitled files? (Too lazy to check)

Uri for untitled document is in the form of untitled:Untitled-1.

Also, there are other potential uri format like vscode-notebook-cell://home/ken/test.Rmd#000001 to represent a VS Code notebook cell in a notebook editor.

I updated the test util functions by supporting uri input directly.