ci: run the Spread tests with the LXD backend

.github/workflows/spread.yaml

@@ -6,8 +6,15 @@ on:
 
 jobs:
   spread-tests:
-    name: Run Spread tests
-    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        runner:
+          - name: X64
+            runs-on: ubuntu-latest
+          - name: ARM64
+            runs-on: [noble, ARM64, large]
+    name: Run Spread tests | ${{ matrix.runner.name }}
+    runs-on: ${{ matrix.runner.runs-on }}
     steps:
       - uses: actions/checkout@v4
 
@@ -38,13 +45,16 @@ jobs:
         with:
           go-version: '>=1.17.0'
 
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@v3
+      - name: Install LXD
+        uses: canonical/[email protected]
+        with:
+            channel: 5.21/stable
 
       - name: Prepare Spread suites
         id: spread-suites
         env:
           integration-tests: "tests/spread/integration"
+          backend: "lxd"
         run: |
           set -ex
           spread_tasks=""
@@ -54,7 +64,7 @@ jobs:
             pkg_tests="${{ env.integration-tests }}/${pkg_name}"
             if [ -f "${pkg_tests}/task.yaml" ] && [[ $spread_tasks != *"${pkg_tests}"* ]]
             then
-              spread_tasks="${spread_tasks} ${pkg_tests}"
+              spread_tasks="${spread_tasks} ${{ env.backend }}:${pkg_tests}"
             fi
           done
 

CONTRIBUTING.md

@@ -281,24 +281,31 @@ existing examples, providing at least the `summary` and `execute` fields inside
 [Spread docs](https://github.com/snapcore/spread)),
    1. in `test/spread/lib/` you'll also find a set of helper functions that you
   can call from within your `task.yaml` execution script,
-1. once your test is ready, ensure you have the necessary requirements to run it
-locally:
-    - Docker: you can install it via the [Snap Store](https://snapcraft.io/docker) or
-    by following the [official instructions](https://docs.docker.com/engine/install/)
-    - Spread: we recommend installing it from source (with
-    `go install github.com/snapcore/spread/cmd/spread@latest`), but there's
-    also a [Spread snap](https://snapcraft.io/spread)
-    - QEMU: if testing for multiple architectures, you'll need to install these
-    packages: `sudo apt-get install qemu binfmt-support qemu-user-static`
+1. once your test is ready, ensure you have Spread installed (we recommend installing it from source with
+`go install github.com/snapcore/spread/cmd/spread@latest`, but there's also a
+[Spread snap](https://snapcraft.io/spread)) and also ensure you install the
+necessary requirements to run the tests locally:
+    - with Docker:
+      - Docker: you can install it via the [Snap Store](https://snapcraft.io/docker) or
+      by following the [official instructions](https://docs.docker.com/engine/install/)
+      - QEMU: if testing for multiple architectures, you'll need to install these
+      packages: `sudo apt-get install qemu binfmt-support qemu-user-static`
+
+      or
+    - with LXD:
+      - LXD: [install and configure LXD](https://canonical.com/lxd/install),
 1. from the repository's root directory, you can now run
-`spread tests/spread/integration/<pkg>` for running the tests for your package
-`<pkg>` slices, on all architectures. Additionally, you can also:
-   - run `spread` for orchestrating **all** the tests (not just yours), for all
-  architectures, or
-   - run `spread docker:ubuntu-22.04-amd64` for orchestrating **all** the tests
-   (not just yours) for amd64 only, or
-   - run `spread docker:ubuntu-22.04-arm64v8:tests/spread/integration/<pkg>`
-   for running only the tests for your package `<pkg>` slices, on arm64.
+
+    ```bash
+    spread lxd:tests/spread/integration/<pkgA> lxd:tests/spread/integration/<pkgB> ...
+    ```
+
+    for running the tests for your slices. Additionally, you can also:
+    - replace `lxd` with `docker` to run the tests on all supported
+    architectures (NOTE: the `docker` backend might be unable to run tests that
+    perform privileged operations);
+    - run `spread docker:ubuntu-22.04-amd64` for orchestrating **all** the tests
+    (not just yours) with Docker, for amd64 only. 
 
 #### 8. Open the PR(s)