diff --git a/mmcv/engine/test.py b/mmcv/engine/test.py
index 023ebc4e9f..a1a5bcfcb5 100644
--- a/mmcv/engine/test.py
+++ b/mmcv/engine/test.py
@@ -32,7 +32,6 @@ def single_gpu_test(model, data_loader):
             result = model(return_loss=False, **data)
         results.extend(result)
 
-        # use the first key as main key to calculate the batch size
         batch_size = len(result)
         for _ in range(batch_size):
             prog_bar.update()