Moved analyzer tests to its own project

Also moves tests to `./test` which makes it possible
for all test projects to share the same .editorconfig
files and similar.

test/Spectre.Console.Tests/Data/Commands/DogCommand.cs

@@ -0,0 +1,36 @@
+using System.ComponentModel;
+using System.Linq;
+using Spectre.Console.Cli;
+
+namespace Spectre.Console.Tests.Data
+{
+    [Description("The dog command.")]
+    public class DogCommand : AnimalCommand<DogSettings>
+    {
+        public override ValidationResult Validate(CommandContext context, DogSettings settings)
+        {
+            if (context is null)
+            {
+                throw new System.ArgumentNullException(nameof(context));
+            }
+
+            if (settings is null)
+            {
+                throw new System.ArgumentNullException(nameof(settings));
+            }
+
+            if (settings.Age > 100 && !context.Remaining.Raw.Contains("zombie"))
+            {
+                return ValidationResult.Error("Dog is too old...");
+            }
+
+            return base.Validate(context, settings);
+        }
+
+        public override int Execute(CommandContext context, DogSettings settings)
+        {
+            DumpSettings(context, settings);
+            return 0;
+        }
+    }
+}