Create server at the beginning of pytest test

Question

I would like to create server before tests start and then terminate it after all tests run. Description of behaviour below.

First time I run tests:
1. Returns error (below)
2. Tests fail
3. Server is invoked (now server is running)

Second time I run tests:
1. Returns the same error (below)
2. Tests pass
3. Server is shutdown

Error: Exception has occurred: RuntimeError Could not start process server

@pytest.fixture(autouse=True, scope="session")
def start_server(xprocess):
    port = 8000
    server_path = py.path.local(__file__).dirpath("service.py")
    xprocess.ensure("server", lambda cwd: ("started", [sys.executable, server_path, port]))
    yield
    xprocess.getinfo("server").terminate()

Answer 1

For future reference, this is the exact application of pytest-xprocess plugin. You could write a simple fixture like the following to start an instance of your server and make it available in your tests:

# content of conftest.py

import pytest
from xprocess import ProcessStarter

@pytest.fixture
def myserver(xprocess):
    class Starter(ProcessStarter):
        # startup pattern
        pattern = "PATTERN"

        # command to start process
        args = ['command', 'arg1', 'arg2']

    # ensure process is running and return its logfile
    logfile = xprocess.ensure("myserver", Starter)

    conn = # create a connection or url/port info to the server
    yield conn

    # clean up whole process tree afterwards
    xprocess.getinfo("myserver").terminate()