docs: Add general README for tests section

This PR adds general README documentation for the tests section
in the kata containers repository.

Fixes #9209

Signed-off-by: Gabriela Cervantes <gabriela.cervantes.tellez@intel.com>

tests/README.md

@@ -0,0 +1,53 @@
+# Kata Containers Tests
+
+This directory contains various types of tests for testing the Kata Containers
+repository.
+
+## Test Content
+
+We provide several tests to ensure Kata-Containers run on different scenarios
+and with different container managers.
+
+1. Integration tests to ensure compatibility with:
+   - [Kubernetes](https://github.com/kata-containers/kata-containers/tree/main/tests/integration/kubernetes)
+   - [Cri-Containerd](https://github.com/kata-containers/kata-containers/tree/main/tests/integration/cri-containerd)
+   - [Docker](https://github.com/kata-containers/kata-containers/tree/main/tests/integration/docker)
+   - [Nerdctl](https://github.com/kata-containers/kata-containers/tree/main/tests/integration/nerdctl)
+   - [Nydus](https://github.com/kata-containers/kata-containers/tree/main/tests/integration/nydus)
+   - [Runk](https://github.com/kata-containers/kata-containers/tree/main/tests/integration/runk)
+2. [Stability tests](https://github.com/kata-containers/kata-containers/tree/main/tests/stability)
+3. [Metrics](https://github.com/kata-containers/kata-containers/tree/main/tests/metrics)
+4. [Functional](https://github.com/kata-containers/kata-containers/tree/main/tests/functional)
+
+## GitHub Actions
+
+Kata Containers uses GitHub Actions in the [Kata Containers](https://github.com/kata-containers/kata-containers) repository.
+
+## Breaking Compatibility
+
+In case the patch you submit breaks the CI because it needs to be tested
+together with a patch from another `kata-containers` repository, you have to
+specify which repository and which pull request it depends on.
+
+Using a simple tag `Depends-on:` in your commit message will allow the CI to
+run properly. Notice that this tag is parsed from the latest commit of the
+pull request.
+
+For example:
+
+```
+	Subsystem: Change summary
+
+	Detailed explanation of your changes.
+
+	Fixes: #nnn
+
+	Depends-on:github.com/kata-containers/kata-containers#999
+
+	Signed-off-by: <contributor@foo.com>
+
+```
+
+In this example, we tell the CI to fetch the pull request 999 from the `kata-containers`
+repository and use that rather than the `main` branch when testing the changes
+contained in this pull request.