diff --git a/src/shared/protocol.test.ts b/src/shared/protocol.test.ts
new file mode 100644
index 0000000..9423a2a
--- /dev/null
+++ b/src/shared/protocol.test.ts
@@ -0,0 +1,63 @@
+import { Protocol } from "./protocol.js";
+import { Transport } from "./transport.js";
+import {
+  McpError,
+  ErrorCode,
+  Request,
+  Result,
+  Notification,
+} from "../types.js";
+import { ZodType, z } from "zod";
+
+// Mock Transport class
+class MockTransport implements Transport {
+  onclose?: () => void;
+  onerror?: (error: Error) => void;
+  onmessage?: (message: unknown) => void;
+
+  async start(): Promise<void> {}
+  async close(): Promise<void> {
+    this.onclose?.();
+  }
+  async send(_message: unknown): Promise<void> {}
+}
+
+describe("protocol tests", () => {
+  let protocol: Protocol<Request, Notification, Result>;
+  let transport: MockTransport;
+
+  beforeEach(() => {
+    transport = new MockTransport();
+    protocol = new (class extends Protocol<Request, Notification, Result> {
+      protected assertCapabilityForMethod(): void {}
+      protected assertNotificationCapability(): void {}
+      protected assertRequestHandlerCapability(): void {}
+    })();
+  });
+
+  test("should throw a timeout error if the request exceeds the timeout", async () => {
+    await protocol.connect(transport);
+    const request = { method: "example", params: {} };
+    try {
+      const mockSchema: ZodType<{ result: string }> = z.object({
+        result: z.string(),
+      });
+      await protocol.request(request, mockSchema, {
+        timeout: 0,
+      });
+    } catch (error) {
+      expect(error).toBeInstanceOf(McpError);
+      if (error instanceof McpError) {
+        expect(error.code).toBe(ErrorCode.RequestTimeout);
+      }
+    }
+  });
+
+  test("should invoke onclose when the connection is closed", async () => {
+    const oncloseMock = jest.fn();
+    protocol.onclose = oncloseMock;
+    await protocol.connect(transport);
+    await transport.close();
+    expect(oncloseMock).toHaveBeenCalled();
+  });
+});
diff --git a/src/types.ts b/src/types.ts
index 44a44d8..59b055a 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -100,13 +100,13 @@ export const JSONRPCResponseSchema = z
   .strict();
 
 /**
- * An incomplete set of error codes that may appear in JSON-RPC responses.
+ * Error codes defined by the JSON-RPC specification.
  */
 export enum ErrorCode {
   // SDK error codes
-  ConnectionClosed = -1,
-  RequestTimeout = -2,
-
+  ConnectionClosed = -32000,
+  RequestTimeout = -32001,
+ 
   // Standard JSON-RPC error codes
   ParseError = -32700,
   InvalidRequest = -32600,
@@ -1237,4 +1237,4 @@ export type ClientResult = z.infer<typeof ClientResultSchema>;
 /* Server messages */
 export type ServerRequest = z.infer<typeof ServerRequestSchema>;
 export type ServerNotification = z.infer<typeof ServerNotificationSchema>;
-export type ServerResult = z.infer<typeof ServerResultSchema>;
+export type ServerResult = z.infer<typeof ServerResultSchema>;
\ No newline at end of file