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Utility for writing multi-host tests for pytest

Project description

A pytest plugin for multi-host testing.


Downloading
-----------

Release tarballs will be made available for download from Pagure Releases:
https://pagure.io/releases/python-pytest-multihost/

The goal is to include this project in Fedora repositories. Until that happens,
you can use testing builds from COPR – see "Developer links" below.

You can also install using pip:
https://pypi.python.org/pypi/pytest-multihost


Usage
-----

This plugin takes a description of your infrastructure,
and provides, via a fixture, Host objects that commands can be called on.

It is intended as a general base for a framework; any project using it will
need to extend it for its own needs.


The object provided to tests is a Config object, which has (among others)
these attributes::

test_dir – directory to store test-specific data in,
defaults to /root/multihost_tests
ipv6 – true if connecting via IPv6

domains – the list of domains

Hosts to run on are arranged in domains, which have::

name – the DNS name of the domain
type – a string specifying the type of the domain ('default' by default)

config – the Config this domain is part of
hosts – list of hosts in this domain

And the hosts have::

role – type of this host; should encode the OS and installed packages
hostname – fully qualified hostname, usually reachable from other hosts
shortname – first component of hostname
external_hostname – hostname used to connect to this host
ip – IP address

domain – the Domain this host is part of

transport – allows operations like uploading and downloading files
run_command() – runs the given command on the host

For each object – Config, Domain, Host – one can provide subclasses
to modify the behavior (for example, FreeIPA would add Host methods
to run a LDAP query or to install an IPA server).
Each object has from_dict and to_dict methods, which can add additional
attributes – for example, Config.ntp_server.


To use the multihost plugin in tests, create a fixture listing the domains
and what number of which host role is needed::

import pytest
from pytest_multihost import make_multihost_fixture

@pytest.fixture(scope='class')
def multihost(request):
mh = make_multihost_fixture(
request,
descriptions=[
{
'type': 'ipa',
'hosts': {
'master': 1,
'replica': 2,
},
},
],
)
return mh

If not enough hosts are available, all tests that use the fixture are skipped.

The object returned from ``make_multihost_fixture`` only has the "config"
attribute.
Users are expected to add convenience attributes.
For example, FreeIPA, which typically uses a single domain with one master,
several replicas and some clients, would do::

from pytest_multihost import make_multihost_fixture

@pytest.fixture(scope='class')
def multihost(request):
mh = make_multihost_fixture(request, descriptions=[
{
'type': 'ipa',
'hosts': {
'master': 1,
'replica': 1,
'client': 1,
},
},
],
)

# Set convenience attributes
mh.domain = mh.config.domains[0]
[mh.master] = mh.domain.hosts_by_role('master')
mh.replicas = mh.domain.hosts_by_role('replica')
mh.clients = mh.domain.hosts_by_role('client')

# IPA-specific initialization/teardown of the hosts
request.cls().install(mh)
request.addfinalizer(lambda: request.cls().uninstall(mh))

# Return the fixture
return mh


As with any pytest fixture, this can be used by getting it as
a function argument.
For a simplified example, FreeIPA usage could look something like this::

class TestMultihost(object):
def install(self, multihost):
multihost.master.run_command(['ipa-server-install'])

def uninstall(self, multihost):
multihost.master.run_command(['ipa-server-install', '--uninstall'])

def test_installed(self, multihost):
multihost.master.run_command(['ipa', 'ping'])


The description of infrastructure is provided in a JSON or YAML file,
which is named on the py.test command line. For example::

ssh_key_filename: ~/.ssh/id_rsa
domains:
- name: adomain.test
type: test-a
hosts:
- name: master
ip: 192.0.2.1
role: master
- name: replica1
ip: 192.0.2.2
role: replica
- name: replica2
ip: 192.0.2.3
role: replica
external_hostname: r2.adomain.test
- name: client1
ip: 192.0.2.4
role: client
- name: extra
ip: 192.0.2.6
role: extrarole
- name: bdomain.test
type: test-b
hosts:
- name: master.bdomain.test
ip='192.0.2.65
role: master

$ py.test --multihost-config=/path/to/configfile.yaml

To use YAML files, the PyYAML package is required. Without it only JSON files
can be used.


Encoding and bytes/text
-----------------------

When writing files or issuing commands, bytestrings are passed through
unchanged, and text strings (``unicode`` in Python 2) are encoded using
a configurable encoding (``utf-8`` by default).

When reading files, bytestrings are returned by default,
but an encoding can be given to get a test string.

For command output, separate ``stdout_bytes`` and ``stdout_text`` attributes
are provided.
The latter uses a configurable encoding (``utf-8` by default).


Contributing
------------

The project is happy to accept patches!
Please file any patches as Pull Requests on the project's `Pagure repo`_.
Any development discussion should be in Pagure Pull Requests and Issues.


Developer links
---------------

* Bug tracker: https://pagure.io/python-pytest-multihost/issues
* Code browser: https://pagure.io/python-pytest-multihost/tree/master
* git clone https://pagure.io/python-pytest-multihost.git
* Unstable packages for Fedora: https://copr.fedoraproject.org/coprs/pviktori/pytest-plugins/

To release, update version in setup.py, add a Git tag like "v0.3",
and run `make tarball`.
Running `make upload` will put the tarball to Fedora Hosted and PyPI,
and a SRPM on Fedorapeople, if you have the rights.
Running `make release` will upload and fire a COPR build.

.. _Pagure repo: https://pagure.io/python-pytest-multihost


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