CUDA out of memory. Tried to allocate 254.00 MiB (GPU 0; 8.00 GiB total capacity; 6.15 GiB already allocated; 15.44 MiB free; 6.19 GiB reserved in total by PyTorch)

I have successfully run the train.py code , with batch size 4. But, when i try to run the test.py file i got this error 
"CUDA out of memory. Tried to allocate 254.00 MiB (GPU 0; 8.00 GiB total capacity; 6.15 GiB already allocated; 15.44 MiB free; 6.19 GiB reserved in total by PyTorch)"
please help me in solving  this issue. 
  