Explain how to use coverage run (docs)

Fixes #152

docs/testcoverage.rst

@@ -1,21 +1,46 @@
 Test Coverage
 =============
 
-You can integrate Coverage.py with behave-django to find out the test coverage of your code.
+You can integrate `Coverage.py`_ with behave-django to find out the test coverage
+of your code.
 
-Dependencies
-------------
+There are two ways to do this, the simple (and obvious one) via invocation
+through the ``coverage`` CLI binary, and alternatively by coding the integration
+in the ``environment.py`` file of your BDD test setup.
 
-At First, you should install Coverage.py dependency
+.. _Coverage.py: https://coverage.readthedocs.io/
+
+Prerequisites
+-------------
+
+Obviously, you need to install Coverage.py to measure code coverage, e.g.
+
+.. code-block:: bash
+
+ $ pip install coverage[toml]
+
+Invoke via ``coverage``
+-----------------------
+
+Instead of using ``python manage.py`` you simply use ``coverage run manage.py``
+to invoke your BDD tests, e.g.
+
+.. code-block:: bash
+
+ $ coverage run manage.py behave
+
+Afterwards, you can display a coverage report in your terminal to understand
+which lines your tests are missing, e.g.
 
 .. code-block:: bash
 
- $ pip install coverage
+ $ coverage report --show-missing
 
-Environment.py
---------------
+Integrate via ``environment.py``
+--------------------------------
 
-In ``environment.py``, add the code snippet below in the ``before_all`` function to start measuring test coverage:
+In ``environment.py``, add the code snippet below in the ``before_all`` function
+to start measuring test coverage:
 
 .. code-block:: python
 
@@ -37,50 +62,50 @@ You can save the coverage result on html format.
  cov.save()
  cov.html_report(directory="./cov")
 
-
 You can check the test coverage on the web with the following command.
 
 .. code-block:: bash
 
  $ python -m http.server --directory ./cov
- 
-Warning for behave-django
--------------------------
 
-Internally, the time before_all is executed seems to be later than the time when django loads the modules set in each app.
+.. warning::
 
-So sometimes it is necessary to reload django app's modules for accurate test coverage measurement.
+ Internally, the time ``before_all`` is executed seems to be later than the
+ time when django loads the modules set in each app.
 
-Like this:
+ So sometimes it is necessary to reload django app's modules for accurate
+ test coverage measurement.
 
-.. code-block:: python
+ Like this:
 
- import inspect
- import importlib
- 
- def reload_modules():
- import your_app1
- import your_app2
-
- for app in [your_app1, your_app2]:
- members = inspect.getmembers(app)
- modules = map(
- lambda keyval: keyval[1],
- filter(lambda keyval: inspect.ismodule(keyval[1]), members),
- )
- for module in modules:
- try:
- importlib.reload(module)
- except:
- continue
+ .. code-block:: python
 
-.. code-block:: python
+ import inspect
+ import importlib
 
- def before_all(context):
- # cov
- cov = coverage.Coverage()
- cov.start()
- context.cov = cov
+ def reload_modules():
+ import your_app1
+ import your_app2
+
+ for app in [your_app1, your_app2]:
+ members = inspect.getmembers(app)
+ modules = map(
+ lambda keyval: keyval[1],
+ filter(lambda keyval: inspect.ismodule(keyval[1]), members),
+ )
+ for module in modules:
+ try:
+ importlib.reload(module)
+ except:
+ continue
+
+ .. code-block:: python
+
+ def before_all(context):
+ # cov
+ cov = coverage.Coverage()
+ cov.start()
+ context.cov = cov
 
- # modules
- reload_modules()
+  # modules
+  reload_modules()