[Manual Cherry-pick] Add external controlplane e2e test (#676)

docs/README.md

@@ -1587,7 +1587,7 @@ In this setup there is an external control plane cluster (`cluster1`) and a remo
     kubectl wait --context "${CTX_CLUSTER1}" --for=condition=Ready istios/external-istiod --timeout=3m
     ```
 
-8. Create the Istio resources to route traffic from the ingress gateway to the external control plane.
+8. Create the `Gateway` and `VirtualService` resources to route traffic from the ingress gateway to the external control plane.
 
     ```sh
     kubectl apply --context "${CTX_CLUSTER1}" -f - <<EOF

tests/e2e/multicluster/common.go

@@ -1,3 +1,5 @@
+//go:build e2e
+
 // Copyright Istio Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
@@ -16,21 +18,65 @@ package multicluster
 
 import (
 	"fmt"
+	"strings"
+	"text/template"
 	"time"
 
+	"github.com/istio-ecosystem/sail-operator/pkg/istioversion"
+	"github.com/istio-ecosystem/sail-operator/tests/e2e/util/common"
 	"github.com/istio-ecosystem/sail-operator/tests/e2e/util/kubectl"
 	. "github.com/onsi/gomega"
 )
 
+// ClusterDeployment represents a cluster along with its sample app version.
+type ClusterDeployment struct {
+	Kubectl    kubectl.Kubectl
+	AppVersion string
+}
+
+// deploySampleApp deploys the sample apps (helloworld and sleep) in the given cluster.
+func deploySampleApp(k kubectl.Kubectl, ns string, istioVersion istioversion.VersionInfo, appVersion string) {
+	helloWorldYAML := common.GetSampleYAML(istioVersion, "helloworld")
+	Expect(k.WithNamespace(ns).ApplyWithLabels(helloWorldYAML, "service=helloworld")).To(Succeed(), "Sample service deploy failed on Cluster")
+	Expect(k.WithNamespace(ns).ApplyWithLabels(helloWorldYAML, "version="+appVersion)).To(Succeed(), "Sample service deploy failed on Cluster")
+
+	sleepYAML := common.GetSampleYAML(istioVersion, "sleep")
+	Expect(k.WithNamespace(ns).Apply(sleepYAML)).To(Succeed(), "Sample sleep deploy failed on Cluster")
+}
+
+// deploySampleAppToClusters deploys the sample app to all provided clusters.
+func deploySampleAppToClusters(ns string, istioVersion istioversion.VersionInfo, clusters []ClusterDeployment) {
+	for _, cd := range clusters {
+		deploySampleApp(cd.Kubectl, ns, istioVersion, cd.AppVersion)
+	}
+}
+
 // verifyResponsesAreReceivedFromBothClusters checks that when the sleep pod in the sample namespace
-// sends a request to the helloworld service, it receives responses from both v1 and v2 versions,
-// which are deployed in different clusters
-func verifyResponsesAreReceivedFromBothClusters(k kubectl.Kubectl, clusterName string) {
-	expectedVersions := []string{"v1", "v2"}
+// sends a request to the helloworld service, it receives responses from expectedVersions,
+// which can be either "v1" or "v2" on on different clusters.
+func verifyResponsesAreReceivedFromExpectedVersions(k kubectl.Kubectl, expectedVersions ...string) {
+	if len(expectedVersions) == 0 {
+		expectedVersions = []string{"v1", "v2"}
+	}
 	for _, v := range expectedVersions {
 		Eventually(k.WithNamespace("sample").Exec, 10*time.Second, 10*time.Millisecond).
 			WithArguments("deploy/sleep", "sleep", "curl -sS helloworld.sample:5000/hello").
 			Should(ContainSubstring(fmt.Sprintf("Hello version: %s", v)),
-				fmt.Sprintf("sleep pod in %s did not receive any response from %s", clusterName, v))
+				fmt.Sprintf("sleep pod in %s did not receive any response from %s", k.ClusterName, v))
 	}
 }
+
+// genTemplate takes a YAML string with go template annotations and a structure
+// that fills in those annotations and outputs a YAML string with that structure
+// applied to the template.
+// Example: version: {{ .Version }} | {Version: "1.2.3"} --> version: Version: "1.2.3"
+// Any errors will fail the test.
+func genTemplate(manifestTmpl string, values any) string {
+	tmpl, err := template.New("manifest-template").Parse(manifestTmpl)
+	Expect(err).ToNot(HaveOccurred(),
+		"template is likely either malformed YAML or the values do not match what is expected")
+
+	var b strings.Builder
+	Expect(tmpl.Execute(&b, values)).To(Succeed())
+	return b.String()
+}