Documentation tox fix

Added information about debugging unit test with tox.
Replace 3 references to py26 with py34 to reflect current
rally tox configuration.

Co-Authored-By: Illia Khudoshyn <ikhudoshyn@mirantis.com>

Change-Id: I10c865fae473111b35dca1b9c8f51f31ba066b42
closes-bug: 1547265

doc/source/contribute.rst

@@ -64,7 +64,7 @@ Several Linux distributions (notably Fedora 16 and Ubuntu 12.04) are also starti
 
 7. Start coding
 
-8. Run the test suite locally to make sure nothing broke, e.g. (this will run py26/py27/pep8 tests):
+8. Run the test suite locally to make sure nothing broke, e.g. (this will run py34/py27/pep8 tests):
 
 .. code-block:: bash
 
@@ -127,13 +127,41 @@ To run unit tests locally:
   $ pip install tox
   $ tox
 
-To run py26, py27 or pep8 only:
+To run py34, py27 or pep8 only:
 
 .. code-block:: console
 
   $ tox -e <name>
 
-  #NOTE: <name> is one of py26, py27 or pep8
+  #NOTE: <name> is one of py34, py27 or pep8
+
+To run a single unit test e.g. test_deployment
+
+.. code-block:: console
+
+  $ tox -e <name> -- <test_name>
+
+  #NOTE: <name> is one of py34, py27 or pep8
+  #      <test_name> is the unit test case name
+
+To debug issues on the unit test:
+
+- Add breakpoints on the test file using ``import pdb;`` ``pdb.set_trace()``
+- Then run tox in debug mode:
+
+.. code-block:: console
+
+  $ tox -e debug <test_name>
+  #NOTE: use python 2.7
+  #NOTE: <test_name> is the unit test case name
+
+  or 
+
+.. code-block:: console
+
+  $ tox -e debug34 <test_name>
+  #NOTE: use python 3.4
+  #NOTE: <test_name> is the unit test case name
 
 To get test coverage:
 

tox.ini

@@ -35,10 +35,19 @@ basepython = python3.4
 [testenv:venv]
 commands = {posargs}
 
+
+[testenv:debug]
+commands = oslo_debug_helper -t tests {posargs}
+
+[testenv:debug34]
+basepython = python3.4
+commands = oslo_debug_helper -t tests {posargs}
+
 [testenv:cli]
 sitepackages = True
 commands = {toxinidir}/tests/ci/rally-integrated.sh
 
+
 [testenv:cover]
 commands = {toxinidir}/tests/ci/cover.sh {posargs}