Add unit test for duplicate firmware filenames

src/BizHawk.Tests/Emulation.Common/Database/FirmwareDatabaseTests.cs

@@ -1,3 +1,7 @@
+using System.Collections.Generic;
+using System.Linq;
+
+using BizHawk.Common.CollectionExtensions;
 using BizHawk.Common.StringExtensions;
 using BizHawk.Emulation.Common;
 
@@ -20,5 +24,28 @@ static void CustomAssert(string hash)
 			foreach (var hash in FirmwareDatabase.FirmwareFilesByHash.Keys) CustomAssert(hash);
 			foreach (var fo in FirmwareDatabase.FirmwareOptions) CustomAssert(fo.Hash);
 		}
+
+		[TestMethod]
+		public void CheckOrganizeFilenames()
+		{
+			SortedList<string, FirmwareFile> seen = new();
+			List<FirmwareFile> dupes = new();
+			foreach (var ff in FirmwareDatabase.FirmwareFilesByHash.Values)
+			{
+				if (seen.TryGetValue(ff.RecommendedName, out var ffExisting))
+				{
+					dupes.Add(ffExisting);
+					dupes.Add(ff);
+				}
+				else
+				{
+					seen.Add(ff.RecommendedName, ff);
+				}
+			}
+			if (dupes.Count is 0) return;
+			Assert.Fail($"multiple {nameof(FirmwareFile)}s have the same suggested filename (breaks Organize function):\n{
+				string.Join("\n", dupes.Select(static ff => $"\t{ff.RecommendedName} {ff.Hash}").Order())
+			}");
+		}
 	}
 }