I have a model pretrained on ImageNet like this:
from keras.applications import resnet50
model = resnet50.ResNet50(weights='imagenet')
Is there any way to get test ImageNet dataset and their labels (which means data not used for training the above model)?
Sadly ImageNet (from ILSVRC2012) never released the labels for the 100k images in the test dataset. You can use instead the 50k images from the Validation dataset, whose labels can be found in the Develpoment Kit (tasks 1 and 2).
You can download both the Validation images and the validation labels from http://www.image-net.org/challenges/LSVRC/2012/downloads
There is an ImageNet Test set with 100k images available here, and although you cannot access the labels, you can instead predict the labels for all the images and submit your predictions for evaluation (top1, top5) here.