Update tempest hacking regarding unit tests

This commit just updates some of the hacking documentation around unit
tests. It also adds a new hacking rule to ensure that setUpClass isn't
used for the unit tests.

Partially implements bp unit-tests

Change-Id: Ie8b1c9f1312a467265d53bc28ee905fa1b5fbb53

HACKING.rst

@@ -9,8 +9,8 @@ Tempest Specific Commandments
 ------------------------------
 
 - [T102] Cannot import OpenStack python clients in tempest/api tests
-- [T103] tempest/tests is deprecated
 - [T104] Scenario tests require a services decorator
+- [T105] Unit tests cannot use setUpClass
 
 Test Data/Configuration
 -----------------------
@@ -192,3 +192,15 @@ Sample Configuration File
 The sample config file is autogenerated using a script. If any changes are made
 to the config variables in tempest then the sample config file must be
 regenerated. This can be done running the script: tools/generate_sample.sh
+
+Unit Tests
+----------
+Unit tests are a separate class of tests in tempest. They verify tempest
+itself, and thus have a different set of guidelines around them:
+
+1. They can not require anything running externally. All you should need to
+   run the unit tests is the git tree, python and the dependencies installed.
+   This includes running services, a config file, etc.
+
+2. The unit tests cannot use setUpClass, instead fixtures and testresources
+   should be used for shared state between tests.

tempest/hacking/checks.py

@@ -21,6 +21,7 @@ PYTHON_CLIENTS = ['cinder', 'glance', 'keystone', 'nova', 'swift', 'neutron']
 
 PYTHON_CLIENT_RE = re.compile('import (%s)client' % '|'.join(PYTHON_CLIENTS))
 TEST_DEFINITION = re.compile(r'^\s*def test.*')
+SETUPCLASS_DEFINITION = re.compile(r'^\s*def setUpClass')
 SCENARIO_DECORATOR = re.compile(r'\s*@.*services\(')
 
 
@@ -52,6 +53,14 @@ def scenario_tests_need_service_tags(physical_line, filename,
                         "T104: Scenario tests require a service decorator")
 
 
+def no_setupclass_for_unit_tests(physical_line, filename):
+    if 'tempest/tests' in filename:
+        if SETUPCLASS_DEFINITION.match(physical_line):
+            return (physical_line.find('def'),
+                    "T105: setUpClass can not be used with unit tests")
+
+
 def factory(register):
     register(import_no_clients_in_api)
     register(scenario_tests_need_service_tags)
+    register(no_setupclass_for_unit_tests)