Testing file uploads in Flask

Question

I'm using Flask-Testing for my Flask integration tests. I've got a form that has a file upload for a logo that I'm trying to write tests for but I keep getting an error saying: TypeError: 'str' does not support the buffer interface.

I'm using Python 3. The closest answer I have found is this but it's not working for me.

This is what one of my many attempts looks like:

def test_edit_logo(self):     """Test can upload logo."""     data = {'name': 'this is a name', 'age': 12}     data['file'] = (io.BytesIO(b"abcdef"), 'test.jpg')     self.login()     response = self.client.post(         url_for('items.save'), data=data, follow_redirects=True)     })     self.assertIn(b'Your item has been saved.', response.data)     advert = Advert.query.get(1)     self.assertIsNotNone(item.logo) 

How does one test a file upload in Flask?

Answer 1

The issue ended up not being that when one adds content_type='multipart/form-data' to the post method it expect all values in data to either be files or strings. There were integers in my data dict which I realised thanks to this comment.

So the end solution ended up looking like this:

def test_edit_logo(self):     """Test can upload logo."""     data = {'name': 'this is a name', 'age': 12}     data = {key: str(value) for key, value in data.items()}     data['file'] = (io.BytesIO(b"abcdef"), 'test.jpg')     self.login()     response = self.client.post(         url_for('adverts.save'), data=data, follow_redirects=True,         content_type='multipart/form-data'     )     self.assertIn(b'Your item has been saved.', response.data)     advert = Item.query.get(1)     self.assertIsNotNone(item.logo) 

Answer 2

You need two things:

1.) content_type='multipart/form-data' in your .post()
2.) in your data= pass in file=(BytesIO(b'my file contents'), "file_name.jpg")

A full example:

    data = dict(         file=(BytesIO(b'my file contents'), "work_order.123"),     )      response = app.post(url_for('items.save'), content_type='multipart/form-data', data=data)