• How to syntax check python script using py_compile
• How to run python tests using pylint
• How to test python code with pytest.
• How to mesure test coverage with pytest-cov (Pytest plugin for measuring coverage).
• How to automate tests using pytest with TravisCI.
• Automatic coverage reporting with Coveralls.

You can use the module py_compile to validate the syntax of a python script.

python -m py_compile maths.py  

This python script uses an undefined variable

# more a.py 
a
print a

So python can't execute it.

# python a.py 
Traceback (most recent call last):
  File "a.py", line 1, in <module>
    a
NameError: name 'a' is not defined

However py_compile doesnt catch the error. py_compile only helps with syntax error and other basic checks. Python only goes into function during runtime and hence undefined variable cannot be caught using that.

# python -m py_compile a.py 

However, pylint detects this error.

pylint installation:

sudo -s
pip install astroid
pip install isort
pip install pylint

Test your script with pylint:

# pylint a.py -r no
No config file found, using default configuration
************* Module a
C:  1, 0: Missing module docstring (missing-docstring)
W:  1, 0: Statement seems to have no effect (pointless-statement)
E:  1, 0: Undefined variable 'a' (undefined-variable)
E:  2, 6: Undefined variable 'a' (undefined-variable)

Pytest is a testing tool for python.
To test yourself your python code locally using pytest, you first need to install it:

sudo pip install pytest pytest-cov coveralls  

Actually, coveralls installation is not required locally. coveralls is used by Travis CI to push coverage report to the Coveralls service.

https://travis-ci.com/
https://travis-ci.org/
You need a github account.
You can test your code from Github automatically (at each git push) using Travis CI.
Github supports webhook with Travis CI.
Travis CI runs tests every time you push to your GitHub repository.

https://coveralls.io/
Travis pushes the coverage report to Coveralls every time Travis is run.
You can sign in to Travis and coveralls with your github account.

git clone https://github.com/ksator/continuous-integration-with-python.git
cd continuous-integration-with-python/  

This is a testing tool for python.

pytest installation:

pip install pytest

By default, pytest discovers tests by looking at files that have these patterns test_*.py and *_test.py
Type py.test on the command line at your project root directory: Pytest will traverse all your subdirectories, gather up all the test files, run your tests, and provide an output.

maths.py has some function definitions. test_multiple.py has the tests for math.py

The doctest module searches for pieces of text that look like interactive Python sessions and then executes those sessions to verify that they work exactly as shown.
https://docs.python.org/2/library/doctest.html
Pytest supports doctests with the --doctest-modules flag.

maths3.py is using doctests. The tests are in the code comment.

Testing is important, measuring coverage is also important.
Pytest can measure coverage for you with the coverage plugin, found in the pytest-cov package. pytest-cov is a Pytest plugin for measuring coverage.

pytest-cov installation:

pip install pytest-cov

Use the option --cov to mesure coverage.
With the option --cov-report term-missing, we can see which lines are not covered.

To make these tests and reports automatic, we use a github webhook with Travis CI.
Every time you push to your GitHub repository, Travis tests with pytest the repository.
The file .travis.yml has the Travis CI details.
The file requirements.txt has the list of python packages Travis installs.

Our .travis.yml file use the service Coveralls: Travis pushes the coverage report to Coveralls every time it runs, i.e., every time you push something to your GitHub repository.

py.test  
py.test -v  

py.test --cov .  
py.test --cov . -v  

py.test --cov maths.py  
py.test --cov maths.py -v  

py.test --cov-report term-missing --cov .  
py.test --cov-report term-missing --cov . -v  

py.test --cov-report term-missing --cov=maths.py  
py.test --cov-report term-missing --cov=maths.py -v  

py.test --doctest-modules -v  

py.test --doctest-modules --cov .  
py.test --doctest-modules --cov . -v  

py.test --doctest-modules --cov . --cov-report term-missing  
py.test --doctest-modules --cov . --cov-report term-missing -v  

py.test --doctest-modules --cov=maths3.py  
py.test --doctest-modules --cov=maths3.py -v   

py.test --doctest-modules --cov=maths3.py --cov-report term-missing  
py.test --doctest-modules --cov=maths3.py --cov-report term-missing -v  

You can use a setup.cfg file at the root of the project with configuration options (ignore maths2.py, cov-report term-missing, ....) to then invoke your tests with a simple call to py.test.
More details:

• https://ilovesymposia.com/2014/10/13/continuous-integration-in-python-3-set-up-your-test-configuration-files/
• http://pytest.org/latest/customize.html
• http://coverage.readthedocs.io/en/latest/config.html

• introduction to CI with Travis
• introduction to pytest
• python doctest module
• automated tests with pytest
• measuring test coverage
• setting up test configuration files
• using Travis-CI to run your tests automatically with each git push
• continuously check your test coverage using Coveralls
• badge your repo