Added more unit tests.

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

@@ -16,7 +16,7 @@ public static class ApplyFeeHandler
         var dest = await query.FindByIdAsync(99999);
         if (source == null || dest == null)
         {
-            throw new InvalidOperationException($"Cannot process transfer. Account(s) not found.");
+            throw new InvalidOperationException("Cannot process transfer. Account(s) not found.");
         }
 
         return new FeeContext(source, dest, timeProvider.GetUtcNow());