Add spec for Tempest data driven testing

Change-Id: I5f5afab35c6df37ff928178ac4c00d15e3b222e7
Implements: blueprint ddt-testing

specs/tempest/ddt-testing.rst

@@ -0,0 +1,96 @@
+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+===============================
+Data driven testing for Tempest
+===============================
+
+https://blueprints.launchpad.net/tempest/+spec/tempest-ddt
+
+
+Add support for data driven testing within Tempest.
+
+Problem Description
+===================
+
+Currently we see tests with for-loop that iterate through different
+data set. This can be problematic for debugging and in general
+for test separation (See [1] for some samples).
+
+
+Proposed Change
+===============
+
+Using the ddt framework [2] to extract the data out of the tests.
+DDT will dynamically create tests out of the given data set.
+The DDT framework is already heavily used by unit tests within
+the projects.
+
+Example
+-------
+The test before ddt::
+
+   icmp_type_codes = [(3, 2), (3, 0), (8, 0), (0, 0), (11, None)]
+        for icmp_type, icmp_code in icmp_type_codes:
+            self._create_verify_security_group_rule(sg_id, direction,
+                                                    self.ethertype, protocol,
+                                                    icmp_type, icmp_code)
+
+Instead of iterating through a set of data the corresponding ddt code would
+look like::
+
+    @ddt.data((3, 2), (3, 0), (8, 0), (0, 0), (11, None))
+    def test_create_security_group_rule_with_icmp_type_code(self, type_codes):
+        self._create_verify_security_group_rule(sg_id, direction,
+                                                self.ethertype, protocol,
+                                                type_codes[0], type_codes[1])
+
+Performance
+-----------
+
+Any generated test will rerun setUp() and tearDown(). Code on class level
+should work without any change (and no rerun at all). In Tempest the resource
+setup is usually done within class methods which won't effect the performance.
+
+
+Idempotent_id and refstack
+--------------------------
+
+Since refstack should handle generated tests under the same id, it should
+be fine to use the idempotent decorator to uniquely identify the test group.
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignees:
+  Marc Koderer
+
+Milestones
+----------
+
+Target Milestone for completion:
+  mitaka-3
+
+Work Items
+----------
+
+* Implement idempotent_id functionality
+* Port tests
+
+Dependencies
+============
+
+None.
+
+References
+==========
+
+1. https://review.openstack.org/#/c/223953/
+2. https://pypi.python.org/pypi/ddt
+
+.. _config_tempest.py: https://github.com/redhat-openstack/tempest/blob/master/tools/config_tempest.py