upload file with flask test client

gistfile1.py

import unittest
from app import app
from cStringIO import StringIO

class UploadTest(unittest.TestCase):
    def setUp(self):
        self.app = app
        self.app.config['TESTING'] = True
        self.client = self.app.test_client()

    def test_upload(self):
        res = self.client.post('/', data=dict(
            upload_var=(StringIO("hi everyone"), 'test.txt'),
        ))
        assert res.status_code == 200
        assert 'file saved' in res.data

if __name__ == '__main__':
    unittest.main()

@PVinay737 you need to turn tracebacks on so you can see what's causing the 400 error. Here is what I've used in the past to do that:

https://github.com/lost-theory/moviepicker/blob/be36832/tests/__init__.py#L24

There's also a note on this in the flask docs on testing:

http://flask.pocoo.org/docs/0.12/testing/

Additionally during setup the TESTING config flag is activated. What it does is disable the error catching during request handling so that you get better error reports when performing test requests against the application.

Once you see the underlying traceback (instead of just the 400 error code) you will be able to see where the bug is (either in the way you're making the request in the test code, or if there's a problem in the view code, or something else).