/// <summary>
 /// Initializes a new instance of the <see cref="SelfTestMiddleware"/> class.
 /// </summary>
 /// <param name="next">The next middleware.</param>
 /// <param name="options">The options.</param>
 /// <exception cref="ArgumentNullException"><paramref name="options"/> is <see langword="null" />.</exception>
 public SelfTestMiddleware(Func<IDictionary<string, object>, Task> next, SelfTestMiddlewareOptions options)
 {
     if (options == null)
     {
         throw new ArgumentNullException(nameof(options));
     }
     _next = next;
     _options = options;
 }
 /// <summary>
 /// Uses the <see cref="SelfTestMiddleware">self test middleware</see>.
 /// </summary>
 /// <param name="app">The application.</param>
 /// <param name="options">The options.</param>
 /// <returns>IAppBuilder.</returns>
 public static IAppBuilder UseSelfTestMiddleware(this IAppBuilder app, SelfTestMiddlewareOptions options)
 {
     app.Use<SelfTestMiddleware>(options);
     return app;
 }