Add helm chart linting and snapshot testing (#407)

Implementation based on
azimuth-cloud/cluster-api-janitor-openstack#192

---------

Co-authored-by: Scott Davidson <[email protected]>

Author: Alex-Welsh

.github/workflows/helm-lint.yaml

@@ -0,0 +1,44 @@
+# NOTE: This workflow can be run locally using https://github.com/nektos/act with:
+# act -W .github/workflows/helm-lint.yaml workflow_call -s GITHUB_TOKEN=$(gh auth token)
+name: Helm Lint
+on:
+  workflow_call:
+    inputs:
+      ref:
+        type: string
+        description: The Git ref under test.
+        required: true
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ inputs.ref }}
+          fetch-depth: 0
+
+      - name: Set up Helm
+        uses: azure/setup-helm@v4
+        with:
+          version: v3.15.3
+
+      - name: Set up chart-testing
+        uses: helm/chart-testing-action@v2
+
+      - name: Run chart-testing (lint)
+        run: |-
+          ct lint \
+            --target-branch ${{ github.event.repository.default_branch }} \
+            --charts chart/ \
+            --validate-maintainers=false
+
+      - name: Run template validation
+        run: |-
+          helm template foo chart \
+            | docker run -i --rm ghcr.io/yannh/kubeconform:latest \
+            --strict --summary
+
+      - name: Run manifest snapshot test
+        run: docker run -i --rm -v $(pwd):/apps helmunittest/helm-unittest chart

.github/workflows/test-pr.yaml

@@ -24,6 +24,12 @@ jobs:
     with:
       ref: ${{ github.event.pull_request.head.sha }}
 
+  # Run the chart linting on every PR, even from external repos
+  lint:
+    uses: ./.github/workflows/lint.yaml
+    with:
+      ref: ${{ github.event.pull_request.head.sha }}
+
   # This job exists so that PRs from outside the main repo are rejected
   fail_on_remote:
     runs-on: ubuntu-latest

CONTRIBUTING.md

@@ -0,0 +1,22 @@
+# Contributing
+
+We welcome contributions and suggestions for improvements to this code base.
+Please check for relevant issues and PRs before opening a new one of your own.
+
+## Making a contribution
+
+### Helm template snapshots
+
+The CI in this repository uses the Helm
+[unittest](https://github.com/helm-unittest/helm-unittest) plugin's
+snapshotting functionality to check PRs for changes to the templated manifests.
+Therefore, if your PR makes changes to the manifest templates or values, you
+will need to update the saved snapshots to allow your changes to pass the
+automated tests. The easiest way to do this is to run the helm unittest command
+inside a docker container from the repo root.
+
+```
+docker run -i --rm -v $(pwd):/apps helmunittest/helm-unittest chart -u
+```
+
+where the `-u` option is used to update the existing snapshots.

chart/.helmignore

@@ -21,3 +21,5 @@
 .idea/
 *.tmproj
 .vscode/
+# Helm unit-test files
+tests/

chart/files/api/settings/01-django.yaml

@@ -1,4 +1,4 @@
-SECRET_KEY: {{ .Values.settings.secretKey | default (randAlphaNum 64) }}
+SECRET_KEY: {{ .Values.settings.secretKey | required "No Django secret key specified"  }}
 DEBUG: {{ .Values.settings.debug }}
 CSRF_COOKIE_SECURE: {{ .Values.ingress.tls.enabled }}
 {{- with .Values.settings.csrfCookieName }}