Data Driven Assignment Unit Testing

bp data-driven-tests

Improve our ability to do detailed role assignment testing using a data driven test formats as opposed to acres of method calls.

Problem Description

In many ways, the core function of keystone is to store and provide access to the role assignments on the artifacts that keystone understands (i.e. projects, domains). As keystone deployments scale up, we are continually adding more advanced support for assignment access, as well as pushing more and more intelligence into the drivers for efficiency (e.g. filtering). The use of inheritance and project hierarchies only makes this even more complicated. As we expand this functionality, the core complexity in the assignments engine actually comes down to the list role assignments method. This single backend method will be called for a wide variety of uses (CRUD API response, token generation, federation mapping etc.).

Given how crucial this support will be, we need to ensure our unit testing keeps pace with this. In the past we have written our unit testing simply as pages of method calls to the backends, but this becomes unwieldy and hard to understand and maintain given the numerous filtering options and scenarios that are now supported.

It would be preferable if we had a more compact and see-at-a-glance method of writing the increased testing required in this area.

Proposed Change

While we could go ahead and boil the ocean here and write a full on natural language test engine, it is proposed that we use a simple data driven dictionary approach for defining a test plan. For example a very simple test plan might be:

test_plan = {
    'entities': {'domain': [{'contents': {'user': 1, 'group': 1,
                                          'project': 1}}],
                 'role': 2},
    'assignments': [{'user': 0, 'role': 0, 'domain': 0},
                    {'user': 0, 'role': 1, 'project': 0}],
    'tests': [
        {'params': {},
         'results': [{'user': 0, 'role': 0, 'domain': 0},
                     {'user': 0, 'role': 1, 'project': 0}]},
        {'params': {'role': 1},
         'results': [{'user': 0, 'role': 1, 'project': 0}]}

The above says:

  • Create a domain entity, with 1 user, group and project within it. Also create 2 roles. All entities created can be referred to via an index, that states from zero and is incremented in the order they appear in the test plan
  • Make 2 assignments, i.e. give user 0 the role 0 on domain 0 and also give that same user role 1 on project 0.
  • Run two list role assignment tests (by calling the assignment manager call list_role_assignments), the first test with no parameters and checking that it returns the correct two assignments, and a second test passing in a filter for only returning assignments with role index 1.

The test helper that drives the above test plan obviously turns entity indexes into real entity IDs for calling the actual driver method.

An implementation of the above test plan format and helper was actually posted in the Kilo cycle as a series of patches to support the migration of filtering on the list assignment method into the backend. In the end we deferred this support to Liberty, so now is the time to decide on the type of testing we want for this.

The following set of Kilo patches added increasing support for this data driven methodology and actually found numerous defects during the development of the proposed new list role assignment backend method. It is clear that something like this is required.

The above patches implement adding support for:

  • Using existing entities
  • “Effective mode” in list role assignments
  • Groups
  • Inheritance and project hierarchies


As discussed above, we could write a more complex natural language processor test system - but since this is a test tool for internal development and we need to balance how much code is in the tool vs the tests it is replacing. There are a couple of issues here. The first is that ideally we don’t want to have a test helper that is so complex that it itself needs to be tested in its own right. Second, we should be conscious of performance. Being a pure data defined test approach, the current proposal is really creating a set of directed loops straight from the data supplied. This is often what testers do manually anyway - so there should be little impact on test performance with this approach. A solution that required more processing of a test plan in order to turn it into manager calls would likely have more of an impact on performance.

We could also make the test plan more generic - for instance, maybe there are other backend methods that we might want to apply that too. It is proposed that we solve the problem at hand, then consider any such changes in the future.

Data Model Impact




Security Impact


Notifications Impact


Other End User Impact


Performance Impact

The performance impact of running tests should be minimal, since we are basically using a dictionary to drive a set of directed loops.

Other Deployer Impact


Developer Impact




Primary assignee:

Work Items

The code of the above is already written, so we simply need to rebase it all.





Documentation Impact