"Run Test" code lens issues bare "cargo run"

[FallenWarrior2k]

As the title says, triggering a "Run Test" CodeLens action issues a bare cargo run in a new terminal window instead of executing the specified test.

This can be reproduced as follows:

1. Create a minimal vimrc (e.g. mini.vim) with the following contents (inspired by coc.nvim issue template):

set nocompatible
set runtimepath^=/path/to/coc.nvim
filetype plugin indent on
syntax on
set hidden
nmap <F2> <Plug>(coc-codelens-action)

2. Create a minimal project with cargo new --lib asdf.
3. Open the source file with nvim -u mini.vim asdf/src/lib.rs.
4. Trigger the "Run Test" CodeLens once it shows up.

As I wasn't able to find anything pertaining to CodeLens in this repo, I'm guessing this is an issue somewhere deeper down, but I am not familiar enough with the coc.nvim ecosystems to make an educated guess as to where that might be.
To make sure this wasn't an issue with the RLS itself, I also installed the RLS extension for VSCode, which correctly executed just that one test.