[TestServer] Fix 488 and add simple test lambda

Package.swift

@@ -85,6 +85,12 @@ let package = Package(
                 .byName(name: "AWSLambdaTesting")
             ]
         ),
+        .executableTarget(
+            name: "HelloWorldLambda",
+            dependencies: [
+                "AWSLambdaRuntime"
+            ]
+        ),
         // for perf testing
         .executableTarget(
             name: "MockServer",

Sources/AWSLambdaRuntimeCore/Lambda+LocalServer.swift

@@ -352,33 +352,44 @@ private struct LambdaHTTPServer {
         // :requestID/response endpoint is called by the lambda posting the response
         case (.POST, let url) where url.hasSuffix(Consts.postResponseURLSuffix):
             let parts = head.uri.split(separator: "/")
-            guard let requestId = parts.count > 2 ? String(parts[parts.count - 2]) : nil else {
+            guard let requestID = parts.count > 2 ? String(parts[parts.count - 2]) : nil else {
                 // the request is malformed, since we were expecting a requestId in the path
                 return .init(status: .badRequest)
             }
             // enqueue the lambda function response to be served as response to the client /invoke
-            logger.trace("/:requestID/response received response", metadata: ["requestId": "\(requestId)"])
+            logger.trace("/:requestID/response received response", metadata: ["requestId": "\(requestID)"])
             await self.responsePool.push(
                 LocalServerResponse(
-                    id: requestId,
+                    id: requestID,
                     status: .ok,
                     headers: [("Content-Type", "application/json")],
                     body: body
                 )
             )
 
             // tell the Lambda function we accepted the response
-            return .init(id: requestId, status: .accepted)
+            return .init(id: requestID, status: .accepted)
 
         // :requestID/error endpoint is called by the lambda posting an error response
         // we accept all requestID and we do not handle the body, we just acknowledge the request
         case (.POST, let url) where url.hasSuffix(Consts.postErrorURLSuffix):
             let parts = head.uri.split(separator: "/")
-            guard let _ = parts.count > 2 ? String(parts[parts.count - 2]) : nil else {
+            guard let requestID = parts.count > 2 ? String(parts[parts.count - 2]) : nil else {
                 // the request is malformed, since we were expecting a requestId in the path
                 return .init(status: .badRequest)
             }
-            return .init(status: .ok)
+            // enqueue the lambda function response to be served as response to the client /invoke
+            logger.trace("/:requestID/response received response", metadata: ["requestId": "\(requestID)"])
+            await self.responsePool.push(
+                LocalServerResponse(
+                    id: requestID,
+                    status: .internalServerError,
+                    headers: [("Content-Type", "application/json")],
+                    body: body
+                )
+            )
+
+            return .init(status: .accepted)
 
         // unknown call
         default:

Sources/HelloWorldLambda/main.swift

@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftAWSLambdaRuntime open source project
+//
+// Copyright (c) 2025 Apple Inc. and the SwiftAWSLambdaRuntime project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftAWSLambdaRuntime project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import AWSLambdaRuntime
+
+struct Request: Codable {
+    var name: String
+}
+
+struct Response: Codable {
+    var greeting: String
+}
+
+let runtime = LambdaRuntime { (_ request: Request, context) -> Response in
+    Response(greeting: "Hello \(request.name)")
+}
+
+try await runtime.run()