Merge #261

261: Add heavy test for code actions r=matklad a=flodiebold

Here's the test for the code actions; I didn't find anything fitting on crates.io ([assert-json-diff](https://crates.io/crates/assert-json-diff) looks kind of nice, but doesn't have anything like the wildcards), so I copied the cargo code as you suggested.

Co-authored-by: Florian Diebold <florian.diebold@freiheit.com>