Unit tests for a couple of commands.

Fix a couple of unused-allocation issues.

source/TextBlade.Core.Tests/Commands/DoNothingCommandTests.cs

@@ -0,0 +1,15 @@
+using NUnit.Framework;
+using TextBlade.Core.Commands;
+
+namespace TextBlade.Core.Tests.Commands;
+
+[TestFixture]
+public class DoNothingCommandTests
+{
+    [Test]
+    public void Execute_DoesNothing_Literally()
+    {
+        // Arrange/Act/Assert
+        Assert.That(new DoNothingCommand().Execute(null, null), Is.Empty);
+    }
+}

source/TextBlade.Core.Tests/Commands/ShowHelpCommandTests.cs

@@ -0,0 +1,24 @@
+using NUnit.Framework;
+using TextBlade.Core.Commands;
+
+namespace TextBlade.Core.Tests.Commands;
+
+[TestFixture]
+public class ShowHelpCommandTests
+{
+    [Test]
+    public void Execute_ReturnsABunchOfCommands()
+    {
+        // Arrange/Act
+        var actuals = new ShowHelpCommand().Execute(null, null);
+
+        // Assert
+        // Check a bunch of commands
+        foreach (var expectedCommand in new string[] {"credits", "help", "quit"})
+        {
+            var expected = $"[red]{expectedCommand}[/]".ToUpperInvariant();
+            var actual = actuals.Single(a => a.ToUpperInvariant().Contains(expected));
+            Assert.That(actual.ToUpperInvariant(), Does.Contain(expected));
+        }
+    }
+}

source/TextBlade.Core/Commands/DoNothingCommand.cs

@@ -7,6 +7,6 @@ public class DoNothingCommand : ICommand
 {
     public IEnumerable<string> Execute(IGame game, List<Character> party)
     {
-        return new string[0];
+        return Array.Empty<string>();
     }
 }

source/TextBlade.Core/Commands/QuitGameCommand.cs

@@ -13,11 +13,11 @@ public IEnumerable<string> Execute(IGame game, List<Character> party)
         if (input.KeyChar != 'y' && input.KeyChar != 'Y')
         {
             Console.WriteLine("Cancelling ...");
-            return new string[0];
+            return Array.Empty<string>();
         }
 
         Console.WriteLine("Bye!");
         Environment.Exit(0);
-        return null; // Makes compiler go brrrr
+        return null; // Unreachable code. Makes compiler go brrrr.
     }
 }