testing paramiko in python3

Question

I have a method thus:

def ftp_fetch(self, hostname=None, username=None, password=None, file_name=None):
        source_data = ''
        if hostname and username and password and file_name:
            ssh = paramiko.SSHClient()
            ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
            try:
                ssh.connect(hostname, username=username, password=password)
            except paramiko.SSHException:
                print("Connection Error")
            sftp = ssh.open_sftp()
            source_data = json.loads(
                sftp.file(file_name).read()
            )
            ssh.close()
            return source_data
        return False

... and a test thus:

@patch('paramiko.SSHClient')
def test_ftp_fetch(mock_ssh):
    test_content = '{"date": "06/02/2020", "time": "07:55", "floors":[{"floor": "地面", "capacity": 149, "occupancy": "20"},{"floor": "قبو", "capacity": 184, "occupancy": "20"}]}'
    mock_ssh.open_sftp().file().read().return_string = test_content
    foo = PreProcessor(code="foo")
    response = foo.ftp_fetch()
    assert response == False
    response = foo.ftp_fetch(hostname='http://foo/', username='foo', password = 'bar', file_name = 'baz')
   assert response == json.loads(test_content)

No matter what I've tried to do with the mock I get the same error:

___________________________________________________________________________ test_ftp_fetch ___________________________________________________________________________

mock_ssh = <MagicMock name='SSHClient' id='139650132358312'>

    @patch('paramiko.SSHClient')
    def test_ftp_fetch(mock_ssh):
        test_content = '{"date": "06/02/2020", "time": "07:55", "floors":[{"floor": "地面", "capacity": 149, "occupancy": "20"},{"floor": "قبو", "capacity": 184, "occupancy": "20"}]}'
        mock_ssh.open_sftp().file().read().return_string = test_content
        foo = PreProcessor(code="foo")
        response = foo.ftp_fetch()
        assert response == False
>       response = foo.ftp_fetch(hostname='http://foo/', username='foo', password = 'bar', file_name = 'baz')

preprocessors/test_preprocessors.py:339: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
preprocessors/preprocessors.py:229: in ftp_fetch
    sftp.file(file_name).read()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

s = <MagicMock name='SSHClient().open_sftp().file().read()' id='139650131723376'>, encoding = None, cls = None, object_hook = None, parse_float = None
parse_int = None, parse_constant = None, object_pairs_hook = None, kw = {}
<< snip lots of doc text >>
        if isinstance(s, str):
            if s.startswith('\ufeff'):
                raise JSONDecodeError("Unexpected UTF-8 BOM (decode using utf-8-sig)",
                                      s, 0)
        else:
            if not isinstance(s, (bytes, bytearray)):
                raise TypeError('the JSON object must be str, bytes or bytearray, '
>                               'not {!r}'.format(s.__class__.__name__))
E               TypeError: the JSON object must be str, bytes or bytearray, not 'MagicMock'

/usr/lib/python3.6/json/__init__.py:348: TypeError

So my question is simple:

How do I set up the mock so that the sftp read returns the text defined? (I'm using python 3.6 & pytest)

((and yes, I always try to test with high-order unicode text, even if I don't expect it in normal use))

Answer 1

• Use the MonkeyPatch for better mocking.
• Example:

def test_user_details(monkeypatch):
        mommy.make('Hallpass', user=user)
        return_data = 
            {
            'user_created':'done'
            }
        monkeypatch.setattr(
            'user.create_user', lambda *args, **kwargs: return_data)
        user_1 = create_user(user="+123456789")
        assert user_1.return_data == return_data

Pass monkeypatch as argument to the test and pass the desired method you want o mock on monkeypatch function on test with required return data as you need.

Make sure you install monkey patch pip install monkeypatch