Improve testing and some cleanup refactoring.

wolverine/a-frame-architecture/FinancialApi.Application/Handlers/TransferFundsHandler.cs

@@ -20,7 +20,10 @@ public static class TransferFundsHandler
         var source = await query.FindByIdAsync(cmd.SourceAccountId);
         var dest = await query.FindByIdAsync(cmd.DestinationAccountId);
 
-        if (source == null || dest == null) return null;
+        if (source == null || dest == null)
+        {
+            return null;
+        }
 
         return new TransferContext(source, dest, timeProvider.GetUtcNow());
     }
@@ -28,8 +31,8 @@ public static class TransferFundsHandler
     public static ( IStorageAction<Account> SourceWrite, IStorageAction<Account> DestWrite, IStorageAction<JournalEntry>
         JournalWrite, FundsTransferredEvent Event ) Handle(TransferFundsCommand cmd, TransferContext context)
     {
-        var updatedSource = context.Source.Debit(cmd.Amount);
-        var updatedDest = context.Destination.Credit(cmd.Amount);
+        var updatedSource = context.Source.ApplyPosting(cmd.Amount, EntryType.Debit);
+        var updatedDest = context.Destination.ApplyPosting(cmd.Amount, EntryType.Credit);
 
         var lines = new List<JournalLine>
         {