Microversion Testing With Tempest

Many OpenStack Services provide their APIs with microversion support and want to test them in Tempest.

This document covers how to test microversions for each project and whether tests should live in Tempest or on project side.

Tempest Scope For Microversion Testing

APIs microversions for any OpenStack service grow rapidly and testing each and every microversion in Tempest is not feasible and efficient way. Also not every API microversion changes the complete system behavior and many of them only change the API or DB layer to accept and return more data on API.

Tempest is an integration test suite, but not all API microversion testing fall under this category. As a result, Tempest mainly covers integration test cases for microversions, Other testing coverage for microversion should be hosted on project side as functional tests or via Tempest plugin as per project guidelines.


Integration tests are those tests which involve more than one service to verify the expected behavior by single or combination of API requests. If a test is just to verify the API behavior as success and failure cases or verify its expected response object, then it does not fall under integration tests.

Tempest will cover only integration testing of applicable microversions with below exceptions:

  1. Test covers a feature which is important for interoperability. This covers tests requirement from Defcore.

  2. Test needed to fill Schema gaps. Tempest validates API responses with defined JSON schema. API responses can be different on each microversion and the JSON schemas need to be defined separately for the microversion. While implementing new integration tests for a specific microversion, there may be a gap in the JSON schemas (caused by previous microversions) implemented in Tempest. Filling that gap while implementing the new integration test cases is not efficient due to many reasons:

    • Hard to review

    • Sync between multiple integration tests patches which try to fill the same schema gap at same time

    • Might delay the microversion change on project side where project team wants Tempest tests to verify the results.

    Tempest will allow to fill the schema gaps at the end of each cycle, or more often if required. Schema gap can be filled with testing those with a minimal set of tests. Those tests might not be integration tests and might be already covered on project side also. This exception is needed because:

    • Allow to create microversion response schema in Tempest at the same time that projects are implementing their API microversions. This will make implementation easier for adding required tests before a new microversion change can be merged in the corresponding project and hence accelerate the development of microversions.

    • New schema must be verified by at least one test case which exercises such schema.

    For example:

    If any projects implemented 4 API microversion say- v2.3, v2.4, v2.5, v2.6 Assume microversion v2.3, v2.4, v2.6 change the API Response which means Tempest needs to add JSON schema for v2.3, v2.4, v2.6. In that case if only 1 or 2 tests can verify all new schemas then we do not need separate tests for each new schemas. In worst case, we have to add 3 separate tests.

  3. Test covers service behavior at large scale with involvement of more deep layer like hypervisor etc not just API/DB layer. This type of tests will be added case by case basis and with project team consultation about why it cannot be covered on project side and worth to test in Tempest.

Project Scope For Microversion Testing

All microversions testing which are not covered under Tempest as per above section, should be tested on project side as functional tests or as Tempest plugin as per project decision.

Configuration options for Microversion

  • Add configuration options for specifying test target Microversions. We need to specify test target Microversions because the supported Microversions may be different between OpenStack clouds. For operating multiple Microversion tests in a single Tempest operation, configuration options should represent the range of test target Microversions. New configuration options are:

    • min_microversion

    • max_microversion

    Those should be defined under respective section of each service. For example:

    min_microversion = None
    max_microversion = latest

How To Implement Microversion Tests

Tempest provides stable interfaces to test API Microversion. For Details, see: API Microversion testing Framework This document explains how to implement Microversion tests using those interfaces.

Step1: Add skip logic based on configured Microversion range

Add logic to skip the tests based on Tests class and configured Microversion range. api_version_utils.check_skip_with_microversion function can be used to automatically skip the tests which do not fall under configured Microversion range. For example:

class BaseTestCase1(api_version_utils.BaseMicroversionTest):

    def skip_checks(cls):
        super(BaseTestCase1, cls).skip_checks()

Skip logic can be added in tests base class or any specific test class depends on tests class structure.

Step2: Selected API request microversion

Select appropriate Microversion which needs to be used to send with API request. api_version_utils.select_request_microversion function can be used to select the appropriate Microversion which will be used for API request. For example:

def resource_setup(cls):
    super(BaseTestCase1, cls).resource_setup()
    cls.request_microversion = (

Step3: Set Microversion on Service Clients

Microversion selected by Test Class in previous step needs to be set on service clients so that APIs can be requested with selected Microversion.

Microversion can be defined as global variable on service clients which can be set using fixture. Also Microversion header name needs to be defined on service clients which should be constant because it is not supposed to be changed by project as per API contract. For example:


class BaseClient1(rest_client.RestClient):
    api_microversion_header_name = 'X-OpenStack-Nova-API-Version'

Now test class can set the selected Microversion on required service clients using fixture which can take care of resetting the same once tests is completed. For example:

def setUp(self):
    super(BaseTestCase1, self).setUp()

Service clients needs to add set Microversion in API request header which can be done by overriding the get_headers() method of rest_client. For example:


class BaseClient1(rest_client.RestClient):
    api_microversion_header_name = 'X-OpenStack-Nova-API-Version'

    def get_headers(self):
        headers = super(BaseClient1, self).get_headers()
            headers[self.api_microversion_header_name] = COMPUTE_MICROVERSION
        return headers

Step4: Separate Test classes for each Microversion

This is last step to implement Microversion test class.

For any Microversion tests, basically we need to implement a separate test class. In addition, each test class defines its Microversion range with class variable like min_microversion and max_microversion. Tests will be valid for that defined range. If that range is out of configured Microversion range then, test will be skipped.


Microversion testing is supported at test class level not at individual test case level.

For example:

Below test is applicable for Microversion from 2.2 till 2.9:

class BaseTestCase1(api_version_utils.BaseMicroversionTest,


class Test1(BaseTestCase1):
    min_microversion = '2.2'
    max_microversion = '2.9'


Below test is applicable for Microversion from 2.10 till latest:

class Test2(BaseTestCase1):
    min_microversion = '2.10'
    max_microversion = 'latest'


Notes about Compute Microversion Tests

Some of the compute Microversion tests have been already implemented with the Microversion testing framework. So for further tests only step 4 is needed.

Along with that JSON response schema might need versioning if needed.

Compute service clients strictly validate the response against defined JSON schema and does not allow additional elements in response. So if that Microversion changed the API response then schema needs to be versioned. New JSON schema file needs to be defined with new response attributes and service client methods will select the schema based on requested microversion.

If Microversion tests are implemented randomly meaning not in sequence order(v2.20 tests added and previous Microversion tests are not yet added) then, still schema might need to be version for older Microversion if they changed the response. This is because Nova Microversion includes all the previous Microversions behavior.

For Example:

Implementing the v2.20 Microversion tests before v2.9 and 2.19- v2.20 API request will respond as latest behavior of Nova till v2.20, and in v2.9 and 2.19, server response has been changed so response schema needs to be versioned accordingly.

That can be done by using the get_schema method in below module:

The base_compute_client module

class BaseComputeClient(auth_provider, service, region, endpoint_type='publicURL', build_interval=1, build_timeout=60, disable_ssl_certificate_validation=False, ca_certs=None, trace_requests='', name=None, http_timeout=None, proxy_url=None, follow_redirects=True)[source]

Base compute service clients class to support microversion.

This class adds microversion to API request header if that is set and provides interface to select appropriate JSON schema file for response validation.

  • auth_provider – An auth provider object used to wrap requests in auth

  • service (str) – The service name to use for the catalog lookup

  • region (str) – The region to use for the catalog lookup

  • kwargs – kwargs required by rest_client.RestClient

Microversion tests implemented in Tempest