Add dummy tests to cover difficult scenarios

CliFx.Tests.Dummy/Program.cs

@@ -0,0 +1,13 @@
+using System.Threading.Tasks;
+
+namespace CliFx.Tests.Dummy
+{
+    public class Program
+    {
+        public static async Task Main() =>
+            await new CliApplicationBuilder()
+                .AddCommandsFromThisAssembly()
+                .Build()
+                .RunAsync();
+    }
+}