Run tests using layers with py.test


Long Story

We have many test suites which use test layers (e. g. the ones from plone.testing). We want to use py.test and all its fancy features to have a modern test runner. There was no way to convert such tests partly: either you have to port the whole project or you are stuck with the zope.testrunner.

On our Pyramid-Sprint Godefroid Chapelle, Thomas Lotze and me wrote a package which wraps layers as py.test fixtures. The result is gocept.pytestlayer.


For each layer it creates two fixtures: one for the layer setUp/tearDown and one for the testSetUp/testTearDown. The layer fixture is configured for class scope but the plug-in orders the tests and knows about the next test so the layer is only torn down if the next test needs another fixture.


You only have to add a new section to your package buildout and running the test via

bin/py.test -x

detects the layers and displays the needed setup code. See the PyPI-Page of the package for details.


Maybe it is possible to get rid of the fixture setup code, so running tests using layers gets even easier.

Viewing scales metrics from Pyramid

We’ve recently started experimenting with the excellent scales library to collect in-process metrics (see Coda Hale’s CodeConf talk “Metrics everywhere” among many others for reasons why one definitely wants to do that).

Scales comes with a flask-based HTTP server that allows viewing the collected measurements and dumping them as JSON. But if you already are in a web application, there’s no real need to spin up yet another thread, open another port etc. to do this. In our case, we’re using Pyramid, so here’s a quick recipe to get the same view that greplin.scales.flaskhandler provides:

Update 2013-11-06: This code is now released as pyramid_scales.

# in your Pyramid setup
config.add_route('scales', '/scales/*prefix')

from StringIO import StringIO
from pyramid.view import view_config
import greplin.scales
import greplin.scales.formats

@view_config(route_name='scales', renderer='string')
def scales_stats(request):
    parts = request.matchdict.get('prefix')
    path = '/'.join(parts)
    stats = greplin.scales.util.lookup(greplin.scales.getStats(), parts)

    output = StringIO()
    outputFormat = request.params.get('format', 'html')
    query = request.params.get('query', None)
    if outputFormat == 'json':
        request.response.content_type = 'application/json'
        greplin.scales.formats.jsonFormat(output, stats, query)
    elif outputFormat == 'prettyjson':
        request.response.content_type = 'application/json'
        greplin.scales.formats.jsonFormat(output, stats, query, pretty=True)
        request.response.content_type = 'text/html'
        # XXX Dear pyramid.renderers.string_renderer_factory,
        # you can't be serious
        request.response.default_content_type = 'not-text/html'
        greplin.scales.formats.htmlHeader(output, '/' + path, __name__, query)
        greplin.scales.formats.htmlFormat(output, tuple(parts), stats, query)

    return output.getvalue()