These files are not meant to be opened or viewed. They are tools. Common formats include:
If you prefer to download a file rather than generate one, several services provide pre-made test files: 2gb sample file
"2 GB sample file"
fallocate -l 2G sample_2gb.file
Does your viewer load Page 1 immediately, or does it hang while downloading the whole 2GB? These files are not meant to be opened or viewed