Developer-specific notes on running unit tests

PYTHON_STYLE_GUIDE.md

@@ -55,12 +55,27 @@ x = 'name: {}; score: {}'.format(name, n)
 we use the `format()` version. The [official Python documentation says](https://docs.python.org/2/library/stdtypes.html#str.format), "This method of string formatting is the new standard in Python 3, and should be preferred to the % formatting described in String Formatting Operations in new code."
 
 
-## Writing (Python) Tests
+## Writing and Running (Python) Unit Tests
 
 We write unit tests for our Python code using the [pytest](http://pytest.org/latest/) framework.
 
 All tests go in the `bigchaindb/tests` directory or one of its subdirectories. You can use the tests already in there as templates or examples.
 
-The BigchainDB Documentation has a [section explaining how to run all unit tests](http://bigchaindb.readthedocs.org/en/master/running-unit-tests.html).
+You can run all unit tests using:
+```text
+py.test -v
+```
+
+or, if that doesn't work, try:
+```text
+python -m pytest -v
+```
+
+or:
+```text
+python setup.py test
+```
+
+If you want to learn about all the things you can do with pytest, see [the pytest documentation](http://pytest.org/latest/).
 
 **Automated testing of pull requests.** We use [Travis CI](https://travis-ci.com/), so that whenever someone creates a new BigchainDB pull request on GitHub, Travis CI gets the new code and does _a bunch of stuff_. You can find out what we tell Travis CI to do in [the `.travis.yml` file](.travis.yml): it tells Travis CI how to install BigchainDB, how to run all the tests, and what to do "after success" (e.g. run `codecov`). (We use [Codecov](https://codecov.io/) to get a rough estimate of our test coverage.)