layer1: add namespace snapshot api step 1

pkg/utils/namespace_test.go

@@ -2,6 +2,7 @@ package utils
 
 import (
 	"os"
+	"reflect"
 	"testing"
 )
 
@@ -177,6 +178,44 @@ func TestNamespaceResolver(t *testing.T) {
 		}
 	})
 
+	t.Run("Snapshot returns stable copy", func(t *testing.T) {
+		nsr := &NamespaceResolver{
+			FissionResourceNS: map[string]string{
+				"ns-b": "ns-b",
+				"ns-a": "ns-a",
+			},
+		}
+
+		snapshot := nsr.Snapshot()
+		expected := []string{"ns-a", "ns-b"}
+		if !reflect.DeepEqual(expected, snapshot) {
+			t.Fatalf("expected snapshot %v, got %v", expected, snapshot)
+		}
+
+		snapshot[0] = "mutated"
+		if nsr.FissionResourceNS["ns-a"] != "ns-a" {
+			t.Fatalf("snapshot mutated internal namespace map")
+		}
+	})
+
+	t.Run("SnapshotWithOptions includes expanded namespaces once", func(t *testing.T) {
+		nsr := &NamespaceResolver{
+			FunctionNamespace: "fn-ns",
+			BuilderNamespace:  "builder-ns",
+			DefaultNamespace:  "default",
+			FissionResourceNS: map[string]string{
+				"default": "default",
+				"user-ns": "user-ns",
+			},
+		}
+
+		snapshot := nsr.SnapshotWithOptions(WithBuilderNs(), WithFunctionNs(), WithDefaultNs())
+		expected := []string{"builder-ns", "default", "fn-ns", "user-ns"}
+		if !reflect.DeepEqual(expected, snapshot) {
+			t.Fatalf("expected snapshot with options %v, got %v", expected, snapshot)
+		}
+	})
+
 	t.Run("getNamespace", func(t *testing.T) {
 		for _, test := range []struct {
 			name                string