Developing Dectate

Install Dectate for development

Clone Dectate from github:

$ git clone

If this doesn’t work and you get an error ‘Permission denied (publickey)’, you need to upload your ssh public key to github.

Then go to the dectate directory:

$ cd dectate

Make sure you have virtualenv installed.

Create a new virtualenv for Python 3 inside the dectate directory:

$ virtualenv -p python3 env/py3

Activate the virtualenv:

$ source env/py3/bin/activate

Make sure you have recent setuptools and pip installed:

$ pip install -U setuptools pip

Install the various dependencies and development tools from develop_requirements.txt:

$ pip install -Ur develop_requirements.txt

For upgrading the requirements just run the command again.

If you want to test Dectate with Python 2.7 as well you can create a second virtualenv for it:

$ virtualenv -p python2.7 env/py27

You can then activate it:

$ source env/py27/bin/activate

Then uprade setuptools and pip and install the develop requirements as described above.


The following commands work only if you have the virtualenv activated.

Running the tests

You can run the tests using py.test:

$ py.test

To generate test coverage information as HTML do:

$ py.test --cov --cov-report html

You can then point your web browser to the htmlcov/index.html file in the project directory and click on modules to see detailed coverage information.

Running the documentation tests

The documentation contains code. To check these code snippets, you can run this code using this command:

(py3) $ sphinx-build -b doctest doc doc/build/doctest

Or alternatively if you have Make installed:

(py3) $ cd doc
(py3) $ make doctest

Or from the Dectate project directory:

(py3) $ make -C doc doctest

Since the sample code in the documentation is maintained in Python 3 syntax, we do not support running the doctests with Python 2.7.

Building the HTML documentation

To build the HTML documentation (output in doc/build/html), run:

$ sphinx-build doc doc/build/html

Or alternatively if you have Make installed:

$ cd doc
$ make html

Or from the Dectate project directory:

$ make -C doc html

Various checking tools

flake8 is a tool that can do various checks for common Python mistakes using pyflakes, check for PEP8 style compliance and can do cyclomatic complexity checking. To do pyflakes and pep8 checking do:

$ flake8 dectate

To also show cyclomatic complexity, use this command:

$ flake8 --max-complexity=10 dectate


With tox you can test Morepath under different Python environments.

We have Travis continuous integration installed on Morepath’s github repository and it runs the same tox tests after each checkin.

First you should install all Python versions which you want to test. The versions which are not installed will be skipped. You should at least install Python 3.5 which is required by flake8, coverage and doctests and Python 2.7 for testing Morepath with Python 2.

One tool you can use to install multiple versions of Python is pyenv.

To find out which test environments are defined for Morepath in tox.ini run:

$ tox -l

You can run all tox tests with:

$ tox

You can also specify a test environment to run e.g.:

$ tox -e py35
$ tox -e pep8
$ tox -e docs