add e2e test for check --pre with templating support

Signed-off-by: Chanwit Kaewkasi <chanwit@gmail.com>

cmd/flux/check_test.go

@@ -0,0 +1,40 @@
+// +build e2e
+
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+	"testing"
+
+	"github.com/fluxcd/flux2/internal/utils"
+	"k8s.io/apimachinery/pkg/version"
+)
+
+func TestCheckPre(t *testing.T) {
+	jsonOutput, err := utils.ExecKubectlCommand(context.TODO(), utils.ModeCapture, rootArgs.kubeconfig, rootArgs.kubecontext, "version", "--output", "json")
+	if err != nil {
+		t.Fatalf("Error running utils.ExecKubectlCommand: %v", err.Error())
+	}
+
+	var versions map[string]version.Info
+	if err := json.Unmarshal([]byte(jsonOutput), &versions); err != nil {
+		t.Fatalf("Error unmarshalling: %v", err.Error())
+	}
+
+	clientVersion := strings.TrimPrefix(versions["clientVersion"].GitVersion, "v")
+	serverVersion := strings.TrimPrefix(versions["serverVersion"].GitVersion, "v")
+
+	cmd := cmdTestCase{
+		args:            "check --pre",
+		wantError:       false,
+		testClusterMode: ExistingClusterMode,
+		templateValues: map[string]string{
+			"clientVersion": clientVersion,
+			"serverVersion": serverVersion,
+		},
+		goldenFile: "testdata/check/check_pre.golden",
+	}
+	cmd.runTestCmd(t)
+}

cmd/flux/main_test.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"path/filepath"
 	"testing"
+	"text/template"
 	"time"
 
 	"github.com/fluxcd/flux2/internal/utils"
@@ -169,6 +170,8 @@ type cmdTestCase struct {
 	objectFile string
 	// TestClusterMode to bootstrap and testing, default to Fake
 	testClusterMode TestClusterMode
+	// TemplateValues enable template preprocessing for the golden file, or golden value
+	templateValues map[string]string
 }
 
 func (cmd *cmdTestCase) runTestCmd(t *testing.T) {
@@ -203,14 +206,28 @@ func (cmd *cmdTestCase) runTestCmd(t *testing.T) {
 
 	var expected string
 	if cmd.goldenValue != "" {
-		expected = cmd.goldenValue
+		if cmd.templateValues != nil {
+			expected, err = executeGoldenTemplate(cmd.goldenValue, cmd.templateValues)
+			if err != nil {
+				t.Fatalf("Error executing golden template: %s", err)
+			}
+		} else {
+			expected = cmd.goldenValue
+		}
 	}
 	if cmd.goldenFile != "" {
-		expectedOutput, err := os.ReadFile(cmd.goldenFile)
+		goldenFileContent, err := os.ReadFile(cmd.goldenFile)
 		if err != nil {
 			t.Fatalf("Error reading golden file: '%s'", err)
 		}
-		expected = string(expectedOutput)
+		if cmd.templateValues != nil {
+			expected, err = executeGoldenTemplate(string(goldenFileContent), cmd.templateValues)
+			if err != nil {
+				t.Fatalf("Error executing golden template file '%s': %s", cmd.goldenFile, err)
+			}
+		} else {
+			expected = string(goldenFileContent)
+		}
 	}
 
 	diff := cmp.Diff(expected, actual)
@@ -219,6 +236,15 @@ func (cmd *cmdTestCase) runTestCmd(t *testing.T) {
 	}
 }
 
+func executeGoldenTemplate(goldenValue string, templateValues map[string]string) (string, error) {
+	tmpl := template.Must(template.New("golden").Parse(goldenValue))
+	var out bytes.Buffer
+	if err := tmpl.Execute(&out, templateValues); err != nil {
+		return "", err
+	}
+	return out.String(), nil
+}
+
 // Run the command and return the captured output.
 func executeCommand(cmd string) (string, error) {
 	args, err := shellwords.Parse(cmd)

cmd/flux/testdata/check/check_pre.golden

@@ -0,0 +1,4 @@
+► checking prerequisites
+✔ kubectl {{ .clientVersion }} >=1.18.0-0
+✔ Kubernetes {{ .serverVersion }} >=1.16.0-0
+✔ prerequisites checks passed