Align cli test Output type with NodeJs type definition

Author: nulltoken

CHANGELOG.md

@@ -12,7 +12,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 ### Changed
 
-- Teach the cli to accept a `issuer-url-trailing-slash` option
+- Teach the cli to accept a `issuer-url-trailing-slash` option (reported in [#353](https://github.com/axa-group/oauth2-mock-server/issues/353) by [Valdermeyder](https://github.com/Valdermeyder))
 - Update dependencies
 
 ## [8.1.0](https://github.com/axa-group/oauth2-mock-server/compare/v8.0.1...v8.1.0) — 2025-06-06

test/lib/child-script.ts

@@ -5,7 +5,7 @@ import type { OAuth2Server } from '../../src';
 interface Output {
   result: OAuth2Server | null;
   err?: unknown;
-  exitCode: number | undefined;
+  exitCode: string | number | undefined;
   stdout: string;
   stderr: string;
 }