How to mock images and other file formats with vfsStream?

Question

I am able to mock text files of any size and images of any resolution.

But for my tests I need images of any resolution and simultaneously of any file size (e.g.: 800x600px and 100 MB) as well as other file formats like PDFs.

When I use LargFileContent the mimetype becomes text/plain.

use org\bovigo\vfs\vfsStream;
use org\bovigo\vfs\content\LargeFileContent;
use Illuminate\Http\UploadedFile

function createImageUploadFile()
{
    $root = vfsStream::setup(
        sys_get_temp_dir()
    );

    $virtualFile = vfsStream::newFile('testFile.jpg')
        ->withContent(LargeFileContent::withMegabytes(100))
        ->at($root);

    // This sets the right mimetype but overwrites the file size
    // imagejpeg(
    //     imagecreate(800, 600),
    //     $virtualFile->url()
    // );

    return new UploadedFile(
        $virtualFile->url(),
        null,
        //mime_content_type($file->url()),
        'image/jpeg', // no impact, remains a text/plain
        null,
        null,
        true
    );
}

How can I generate any type of file (mimetype) of any size and images (png,jpg) of any dimensions and file sizes?