add more tests

lib/socket.ts

@@ -687,10 +687,12 @@ export class Socket<
       );
       if (!isBuffered) {
         // note: handlers that do not accept an error as first argument are ignored here
-        if (this.acks[id].withError) {
-          this.acks[id].call(this, new Error("socket has been disconnected"));
-        }
+        const ack = this.acks[id];
         delete this.acks[id];
+
+        if (ack.withError) {
+          ack.call(this, new Error("socket has been disconnected"));
+        }
       }
     });
   }

test/socket.ts

@@ -678,6 +678,9 @@ describe("socket", () => {
 
             socket.disconnect();
 
+            // @ts-ignore property 'acks' is private
+            expect(Object.keys(socket.acks).length).to.eql(0);
+
             setTimeout(() => success(done, socket), 100);
           });
         });
@@ -693,6 +696,9 @@ describe("socket", () => {
             socket.timeout(10_000).emit("echo", "a", (err) => {
               expect(err).to.be.an(Error);
 
+              // @ts-ignore property 'acks' is private
+              expect(Object.keys(socket.acks).length).to.eql(0);
+
               success(done, socket);
             });
 
@@ -768,6 +774,7 @@ describe("socket", () => {
           socket.once("connect", () => {
             socket.disconnect();
 
+            // the packet will be buffered and sent upon reconnection
             socket.emit("echo", "a", (value) => {
               expect(value).to.eql("a");