Add tests for parsing achievement tags in chat

These tests ensure that `ChatManager.ParseMessage` will not throw on the
server with TShock when given an achievement tag.

TShockLauncher.Tests/ChatTests.cs

@@ -0,0 +1,30 @@
+using Microsoft.Xna.Framework;
+using NUnit.Framework;
+using Terraria.UI.Chat;
+
+namespace TShockLauncher.Tests;
+
+public class ChatTests
+{
+	/// <summary>
+	/// Ensures that the <see cref="Terraria.GameContent.UI.Chat.AchievementTagHandler"/> does not cause exceptions when used on the server.
+	/// </summary>
+	///
+	/// <remarks>The behaviour of TShock regarding the achievement tag handler changes depending on if TShock has
+	/// a <see cref="Terraria.Main"/> instance or not. Therefore, we do not check the correctness of the parsed message, but only if it
+	/// throws an exception.
+	/// </remarks>
+	[TestCase]
+	public void TestChatAchievementTagHandler()
+	{
+		Assert.That(() =>
+		{
+			ChatManager.ParseMessage("No achievement tags", Color.White);
+			ChatManager.ParseMessage("One achievement tag: [a:KILL_THE_SUN]", Color.White);
+			ChatManager.ParseMessage("One achievement tag, using the longer variant: [achievement:KILL_THE_SUN]", Color.White);
+			ChatManager.ParseMessage("Multiple achievement tags: [a:KILL_THE_SUN] and [a:TOPPED_OFF]", Color.White);
+			ChatManager.ParseMessage("One achievement tag, referring to a non-existent achievement: [a:_THIS_WILL_NEVER_EXIST_]", Color.White);
+			ChatManager.ParseMessage("Both valid and invalid achievement tags: [a:KILL_THE_SUN] and [a:_THIS_WILL_NEVER_EXIST_]", Color.White);
+		}, Throws.Nothing);
+	}
+}

TShockLauncher.Tests/TestSetup.cs

@@ -1,5 +1,6 @@
 using NUnit.Framework;
 using Terraria;
+using Terraria.Initializers;
 using Terraria.Localization;
 using TShockAPI;
 
@@ -15,6 +16,8 @@ public class TestSetup
 	[OneTimeSetUp]
 	public static void SetupTShock()
 	{
+		ChatInitializer.Load();
+
 		Program.SavePath = ""; // 1.4.4.2 staticness introduced this where by default it is null, and any touch to Terraria.Main will use it and cause a crash.
 		LanguageManager.Instance.SetLanguage(GameCulture.DefaultCulture); // TShockAPI.Localization will fail without ActiveCulture set
 		Lang.InitializeLegacyLocalization(); // TShockAPI.Localization will fail without preparing NPC names etc