Fix unit test runners via Plenary

[Issafalcon]

Some recent changes to Plenary have led to freezing test scheduling (possibly):

See - kylechui/nvim-surround#246 and https://github.com/folke/noice.nvim/blob/main/tests/init.lua for more details and potential fix

[Issafalcon]

Note that tests fail since updates to the c# treesitter parser (tree-sitter/tree-sitter-c-sharp#338). These need correcting, but the functionality of the plugin is still largely the same (minus the extra namespace node in the tree of file scoped namespaces)