Add new proxy test for random port

This commit adds a new test method `Test_Random_Port` to the `ProxyTests` class. This test ensures that the proxy is able to run and handle traffic on random ports within a valid range.

test/Fluxzy.Tests/ProxyTests.cs

@@ -299,6 +299,20 @@ public async Task Exchange_State_Must_Be_Complete_When_Chunked()
             }
         }
 
+        [Fact]
+        public async Task Test_Random_Port()
+        {
+            var startupSetting = FluxzySetting
+                                 .CreateLocalRandomPort();
+
+            await using var proxy = new Proxy(startupSetting);
+            var endPoints = proxy.Run();
+
+            Assert.Single(endPoints);
+            Assert.True(endPoints.First().Port >= 1000);
+            Assert.True(endPoints.First().Port < 65535);
+        }
+
         [Fact]
         public async Task Test_GetThrough_H1_Plain()
         {
@@ -525,5 +539,6 @@ await response.Content.ReadAsStringAsync(
                 await proxy.DisposeAsync();
             }
         }
+
     }
 }