build-collection.yml: Update contents of testing.md

Update the contents of testing.md so they make sense in a downstream
context.

Signed-off-by: Felix Matouschek <[email protected]>

build-collection.yml

@@ -108,7 +108,42 @@
         - CONTRIBUTING.md
         - docs/CONTRIBUTING.md
         - docs/developing.md
-        - docs/testing.md
+    - name: Set content of downstream testing.md
+      ansible.builtin.copy:
+        dest: "{{ downstream_project }}/docs/testing.md"
+        content: |
+          # Testing
+
+          ## Sanity and unit tests
+
+          Sanity and unit tests can be run with `ansible-test`.
+
+          ### Running tests with ansible-test
+
+          Run sanity tests with `ansible-test` like so:
+
+          ```
+          ANSIBLE_TEST_PREFER_PODMAN=1 ansible-test sanity --docker
+          ```
+
+          Run unit tests with `ansible-test` like so:
+
+          ```
+          ANSIBLE_TEST_PREFER_PODMAN=1 ansible-test units --docker
+          ```
+
+          ## Integration tests
+
+          Integration tests require a working cluster and can be run with
+          `ansible-test`.
+
+          ### Running integration tests with ansible-test
+
+          Run integration tests with `ansible-test` like so:
+
+          ```
+          ansible-test integration
+          ```
     - name: Rebuild downstream collection
       ansible.builtin.command: ansible-galaxy collection build --force .
       args: