tests: introduce golden tests in kong chart using chartsnap (#978)

.gitattributes

@@ -0,0 +1 @@
+charts/kong/ci/__snapshots__/*.snap linguist-generated=true

.github/workflows/release-pr.yaml

@@ -159,6 +159,26 @@ jobs:
       - name: cleanup integration tests (cleanup)
         run: ./scripts/test-env.sh cleanup
 
+  golden-tests:
+    runs-on: ubuntu-latest
+    name: golden-tests
+    steps:
+      - name: checkout
+        uses: actions/checkout@v4
+
+      - name: setup helm
+        uses: azure/setup-helm@v3
+        with:
+          version: v3.11.0
+
+      - name: build helm chart dependency
+        run: |
+          helm repo add bitnami https://charts.bitnami.com/bitnami
+          helm dependency build charts/kong
+
+      - name: run golden tests
+        run: make test.golden
+
   # Workaround to allow checking the matrix tests as required tests without adding the individual cases
   # Ref: https://github.com/orgs/community/discussions/26822#discussioncomment-3305794
   passed:
@@ -168,6 +188,7 @@ jobs:
       - lint-test
       - integration-test
       - oldversion-integration-test
+      - golden-tests
     if: always()
     steps:
       - if: ${{ contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled') }}

Makefile

@@ -6,13 +6,18 @@ _download_tool:
 		GOBIN=$(PROJECT_DIR)/bin go generate -tags=third_party ./$(TOOL).go )
 
 .PHONY: tools
-tools: kube-linter
+tools: kube-linter chartsnap
 
 KUBE_LINTER = $(PROJECT_DIR)/bin/kube-linter
 .PHONY: kube-linter
 kube-linter:
 	@$(MAKE) _download_tool TOOL=kube-linter
 
+.PHONY: chartsnap
+chartsnap:
+	@helm plugin list | grep chartsnap > /dev/null || \
+	helm plugin install https://github.com/jlandowner/helm-chartsnap
+
 .PHONY: lint
 lint: tools lint.charts.kong lint.shellcheck
 
@@ -22,3 +27,24 @@ lint.charts.kong:
 
 lint.shellcheck:
 	shellcheck ./scripts/*
+
+GOLDEN_TEST_CHART ?= kong
+GOLDEN_TEST_CHART_VALUES_DIR ?= ./charts/kong/ci/
+CHARTSNAP_COMMAND = helm chartsnap -c ./charts/$(GOLDEN_TEST_CHART) -f $(GOLDEN_TEST_CHART_VALUES_DIR)
+
+# Defining multi-line strings to echo: https://stackoverflow.com/a/649462/7958339
+define GOLDEN_TEST_FAILURE_MSG
+>> Golden tests have failed.
+>> Please run 'make test.golden.update' to update golden files and commit the changes if they're expected.
+endef
+export GOLDEN_TEST_FAILURE_MSG
+
+.PHONY: test.golden
+test.golden: chartsnap
+	@ $(CHARTSNAP_COMMAND) || \
+	(echo "$$GOLDEN_TEST_FAILURE_MSG" && \
+	exit 1)
+
+.PHONY: test.golden.update
+test.golden.update: chartsnap
+	$(CHARTSNAP_COMMAND) -u

charts/kong/ci/.chartsnap.yaml

@@ -0,0 +1,26 @@
+# It's a configuration file used by helm-chartsnap to ignore dynamically generated fields
+# when comparing the chart's snapshot with the rendered chart.
+# See https://github.com/jlandowner/helm-chartsnap?tab=readme-ov-file#handling-dynamic-values-.
+dynamicFields:
+  - apiVersion: v1
+    kind: Secret
+    name: chartsnap-postgresql
+    jsonPath:
+      - /data/postgres-password
+  - apiVersion: v1
+    kind: Secret
+    name: chartsnap-kong-validation-webhook-keypair
+    jsonPath:
+      - /data/tls.crt
+      - /data/tls.key
+  - apiVersion: v1
+    kind: Secret
+    name: chartsnap-kong-validation-webhook-ca-keypair
+    jsonPath:
+      - /data/tls.crt
+      - /data/tls.key
+  - apiVersion: admissionregistration.k8s.io/v1
+    kind: ValidatingWebhookConfiguration
+    name: chartsnap-kong-validations
+    jsonPath:
+      - /webhooks/0/clientConfig/caBundle