Added error handling for missing data files

tests/UBaseTestCases.pas

@@ -72,9 +72,15 @@ end;
 { TEngineBaseTest }
 
 procedure TEngineBaseTest.Setup;
+var
+  fileName: string;
 begin
   inherited Setup;
   FEngine := TSolverEngine.Create(GetDataPath);
+  fileName := FEngine.GetDataFileName(FSolver);
+  AssertTrue('Cannot find puzzle input file ''' + ExpandFileName(fileName) + '''. '
+    + 'Please download the file from https://adventofcode.com/2023/',
+    FileExists(fileName));
   FEngine.ProcessData(FSolver);
 end;