Add test suite

Author: Peter554

.gitignore

@@ -1,2 +1,3 @@
 /target
 .claude/settings.local.json
+tests/*.pending-snap

CLAUDE.md

@@ -6,10 +6,3 @@ See @README for a general project overview.
 - Look for opportunities to refactor, simplify and improve the code.
 - Ensure that code is documented, and that the documentation is up to date with the code. This includes the README.
 - When you're done making changes test, lint and format the code to check everything (use justfile recipies).
-
-## Testing Guidelines
-
-- All code should have tests (unit and/or integration tests).
-- Use the assert_fs and assert_cmd crates for integration testing.
-- Where parametric tests are appropriate, use the yare crate.
-  Always create a struct (e.g. `Case`) to hold test case data.