Fix incorrect CLI exit code and duplicate error message (#26346)

Follow the CLI refactoring, and add tests.

modules/test/utils.go

@@ -33,3 +33,9 @@ func RedirectURL(resp http.ResponseWriter) string {
 func IsNormalPageCompleted(s string) bool {
 	return strings.Contains(s, `<footer class="page-footer"`) && strings.Contains(s, `</html>`)
 }
+
+func MockVariableValue[T any](p *T, v T) (reset func()) {
+	old := *p
+	*p = v
+	return func() { *p = old }
+}