chore: Move compile-fail tests

Author: Techassi

crates/stackable-versioned-macros/fixtures/README.md

@@ -1,5 +1,8 @@
 # Snapshot Testing
 
+> [!NOTE]
+> Also see the compile-fail tests, described [here](../tests/README.md).
+
 This folder contains fixtures for snapshot testing the `#[versioned()]` macro. Snapshot testing is
 done using the [insta] crate. It provides a [CLI tool][insta-cli] called `cargo-insta` and a
 [VS Code extension][insta-ext].

crates/stackable-versioned-macros/tests/README.md

@@ -0,0 +1,17 @@
+# Compile-Fail Testing
+
+> [!NOTE]
+> Also see the snapshot tests, described [here](../fixtures/README.md).
+
+This type of testing is part of UI testing. These tests assert two things: First, the code should
+**not** compile and secondly should also produce the expected rustc (compiler) error message. For
+this type of testing, we use the [`trybuild`][trybuild] crate.
+
+Tests are currently separated into two folders: `default` and `k8s`. The default test cases don't
+require any additional features to be activated. The Kubernetes specific tests require the `k8s`
+feature to be enabled. These tests can be run with `cargo test --all-features`.
+
+Further information about the workflow are described [here][workflow].
+
+[workflow]: https://docs.rs/trybuild/latest/trybuild/#workflow
+[trybuild]: https://docs.rs/trybuild/latest/trybuild/