[FIXED] Mock a Remote Host in Python

Issue

I am writing some functions, using paramiko, to execute commands and create files on a remote host. I would like to write some unit tests for them, but I don't know what would be the simplest way to achieve this? This is what I envisage as being an example outline of my code:

import os
import paramiko
import pytest

def my_function(hostname, relpath='.', **kwargs):
    ssh = paramiko.SSHClient()
    ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    ssh.connect(hostname, **kwargs)
    sftp = ssh.open_sftp()
    sftp.chdir(relpath)
    stdin, stdout, stderr = ssh.exec_command("echo hallo > test.txt")

@pytest.fixture("module")
def mock_remote_host():
    # start a remote host here with a local test path
    try:
        yield hostname, testpath, {"username":"bob", "password":"1234"}
    finally:
        # delete the test path
        # close the remote host

def test_my_function(mock_remote_host):
    hostname, dirpath, kwargs = mock_remote_host
    my_function(hostname, **kwargs)
    filepath = os.path.join(dirpath, 'test.txt')
    assert os.path.exists(filepath)

I have had a look at the paramiko test modules, but they seem quite complex for my use case and I'm not sure how to go about simplifying them.

Solution

To answer my own question, I have created: https://github.com/chrisjsewell/atomic-hpc/tree/master/atomic_hpc/mockssh.

As the readme discusses; it is based on https://github.com/carletes/mock-ssh-server/tree/master/mockssh with additions made (to implement more sftp functions) based on https://github.com/rspivak/sftpserver

The following changes have also been made:

• revised users parameter, such that either a private_path_key or password can be used
• added a dirname parameter to the Server context manager, such that the this will be set as the root path for the duration of the context.
• patched paramiko.sftp_client.SFTPClient.chdir to fix its use with relative paths.

See test_mockssh.py for example uses.

Answered By - Chris Sewell