Node fs can't access static files

I'm trying to access publicly-accessible static files (both .png and .ttf) through a function in Node. The files exist, and can be accessed through the browser using the URL. For example, accessing

http://localhost:9000/assets/images/thefile.png

resolves the image in a browser.

However, if I try to test the file with fs.stat (pulled from elsewhere on StackOverflow):

fs.stat(testPath, function(err, stat) {
    if(err == null) {
        console.log('File exists');
    } else if(err.code == 'ENOENT') {
        console.log('Error: ', err);
    } else {
        console.log('Some other error: ', err.code);
    }
});

it results in:

Error:  { [Error: ENOENT, stat 'http://localhost:9000/assets/images/thefile.png']
errno: 34,
code: 'ENOENT',
path: 'http://localhost:9000/assets/images/thefile.png' }

Everything else I'm finding relates to not being able to access static files through the browser, but not Node itself trying to access them. I'm hoping someone might know what I'm missing.