add test

Author: jonsequitur

src/System.CommandLine.Tests/CommandExtensionsTests.cs

@@ -0,0 +1,33 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.CommandLine.IO;
+using FluentAssertions;
+using Xunit;
+
+namespace System.CommandLine.Tests
+{
+    public class CommandExtensionsTests
+    {
+        [Fact]
+        public void Mulitple_invocations_via_Invoke_extension_will_not_reconfigure_implicit_parser()
+        {
+            var command = new RootCommand("Root command description")
+            {
+                new Command("inner")
+            };
+
+            var console1 = new TestConsole();
+
+            command.Invoke("-h", console1);
+
+            console1.Out.ToString().Should().Contain(command.Description);
+
+            var console2 = new TestConsole();
+
+            command.Invoke("-h", console2);
+
+            console2.Out.ToString().Should().Contain(command.Description);
+        }
+    }
+}