Add test for CEL reserved symbols without double underscore

Signed-off-by: Omer Aplatony <omerap12@gmail.com>

Kubernetes-commit: 1b371d0d4693da66343aa7f8642a694ea318692d

pkg/cel/escaping_test.go

@@ -19,6 +19,7 @@ package cel
 import (
 	"fmt"
 	"regexp"
+	"strings"
 	"testing"
 
 	fuzz "github.com/google/gofuzz"
@@ -204,3 +205,12 @@ func TestCanSkipRegex(t *testing.T) {
 		})
 	}
 }
+
+func TestCELReservedSymbolsNoDoubleUnderscore(t *testing.T) {
+	for symbol := range celReservedSymbols {
+		if strings.Contains(symbol, "__") {
+			t.Errorf("CEL reserved symbol '%s' contains '__', which is not allowed as it would interfere with escaping", symbol)
+		}
+	}
+}
+