Validate the CsvRenderer

src/render.rs

@@ -784,6 +784,7 @@ impl<S: GenericSim> Renderer<S> for CsvRenderer {
             CsvState::Writing(writer) => writer,
         };
         writer.write_record(row.values()).unwrap();
+        writer.flush().unwrap();
         *lock = Some(CsvState::Writing(writer));
     }
 }