how can I test a neural network ?? #I am a beginner

% I want to test the neural network to run though images in a floder.
% but now it has an error ,Plz show me hor to fix it 
% This network run with Resnet50
% I am really beginner. Thanks a lot


newImage = fullfile('D:\projectLASTYEAR\trainDATA92');
 
 ds = augmentedImageDatastore(imageSize, ...
     newImage,'ColorPreprocessing','gray2rgb');
 
 imageFeatures = activations(net, ds, featureLayer, ...
     'MiniBatchSize', 16, 'OutputAs', 'columns');
 
 Label = predict(classifier,imageFeatures,'ObservationsIn','columns');
  sprintf('The loaded image belongs to %s class', Label)
  
  
%   The error show 
% %   Error using augmentedImageDatastore (line 214)
% %   Invalid input data type.