Tempest Test Writing Guide¶
This guide serves as a starting point for developers working on writing new Tempest tests. At a high level, tests in Tempest are just tests that conform to the standard python unit test framework. But there are several aspects of that are unique to Tempest and its role as an integration test suite running against a real cloud.
This guide is for writing tests in the Tempest repository. While many parts of this guide are also applicable to Tempest plugins, not all the APIs mentioned are considered stable or recommended for use in plugins. Please refer to Tempest Test Plugin Interface for details about writing plugins
Adding a New TestCase¶
The base unit of testing in Tempest is the TestCase (also called the test class). Each TestCase contains test methods which are the individual tests that will be executed by the test runner. But, the TestCase is the smallest self contained unit for tests from the Tempest perspective. It’s also the level at which Tempest is parallel safe. In other words, multiple TestCases can be executed in parallel, but individual test methods in the same TestCase can not. Also, all test methods within a TestCase are assumed to be executed serially. As such you can use the test case to store variables that are shared between methods.
In standard unittest the lifecycle of a TestCase can be described in the following phases:
The setUpClass phase is the first phase executed by the test runner and is used to perform any setup required for all the test methods to be executed. In Tempest this is a very important step and will automatically do the necessary setup for interacting with the configured cloud.
To accomplish this you do not define a setUpClass function, instead there are a number of predefined phases to setUpClass that are used. The phases are:
which is executed in that order. Cleanup of resources provisioned during the resource_setup must be scheduled right after provisioning using the addClassResourceCleanup helper. The resource cleanups stacked this way are executed in reverse order during tearDownClass, before the cleanup of test credentials takes place. An example of a TestCase which defines all of these would be:
from tempest.common import waiters from tempest import config from tempest.lib.common.utils import test_utils from tempest import test CONF = config.CONF class TestExampleCase(test.BaseTestCase): @classmethod def skip_checks(cls): """This section is used to evaluate config early and skip all test methods based on these checks """ super(TestExampleCase, cls).skip_checks() if not CONF.section.foo cls.skip('A helpful message') @classmethod def setup_credentials(cls): """This section is used to do any manual credential allocation and also in the case of dynamic credentials to override the default network resource creation/auto allocation """ # This call is used to tell the credential allocator to not create any # network resources for this test case. It also enables selective # creation of other neutron resources. NOTE: it must go before the # super call cls.set_network_resources() super(TestExampleCase, cls).setup_credentials() @classmethod def setup_clients(cls): """This section is used to setup client aliases from the manager object or to initialize any additional clients. Except in a few very specific situations you should not need to use this. """ super(TestExampleCase, cls).setup_clients() cls.servers_client = cls.os_primary.servers_client @classmethod def resource_setup(cls): """This section is used to create any resources or objects which are going to be used and shared by **all** test methods in the TestCase. Note then anything created in this section must also be destroyed in the corresponding resource_cleanup() method (which will be run during tearDownClass()) """ super(TestExampleCase, cls).resource_setup() cls.shared_server = cls.servers_client.create_server(...) cls.addClassResourceCleanup(waiters.wait_for_server_termination, cls.servers_client, cls.shared_server['id']) cls.addClassResourceCleanup( test_utils.call_and_ignore_notfound_exc( cls.servers_client.delete_server, cls.shared_server['id']))
Since Tempest tests are all about testing a running cloud, every test will need credentials to be able to make API requests against the cloud. Since this is critical to operation and, when running in parallel, easy to make a mistake, the base TestCase class will automatically allocate a regular user for each TestCase during the setup_credentials() phase. During this process it will also initialize a client manager object using those credentials, which will be your entry point into interacting with the cloud. For more details on how credentials are allocated the Test Credentials section of the Tempest Configuration Guide provides more details on the operation of this.
There are some cases when you need more than a single set of credentials, or
credentials with a more specialized set of roles. To accomplish this you have
to set a class variable
credentials on the TestCase directly. For example:
from tempest import test class TestExampleAdmin(test.BaseTestCase): credentials = ['primary', 'admin'] @classmethod def skip_checks(cls): ...
In this example the
TestExampleAdmin TestCase will allocate 2 sets of
credentials, one regular user and one admin user. The corresponding manager
objects will be set as class variables
respectively. You can also allocate a second user by putting ‘alt’ in the
list too. A set of alt credentials are the same as primary but can be used
for tests cases that need a second user/project.
You can also specify credentials with specific roles assigned. This is useful for cases where there are specific RBAC requirements hard coded into an API. The canonical example of this are swift tests which often want to test swift’s concepts of operator and reseller_admin. An actual example from Tempest on how to do this is:
class PublicObjectTest(base.BaseObjectTest): credentials = [['operator', CONF.object_storage.operator_role], ['operator_alt', CONF.object_storage.operator_role]] @classmethod def setup_credentials(cls): super(PublicObjectTest, cls).setup_credentials() ...
In this case the manager objects will be set to
There is no limit to how many credentials you can allocate in this manner, however in almost every case you should not need more than 3 sets of credentials per test case.
To figure out the mapping of manager objects set on the TestCase and the requested credentials you can reference:
By default cls.os_primary is available since it is allocated in the base Tempest test class (located in tempest/test.py). If your TestCase inherits from a different direct parent class (it’ll still inherit from the BaseTestCase, just not directly) be sure to check if that class overrides allocated credentials.
Dealing with Network Allocation¶
When Neutron is enabled and a testing requires networking this isn’t normally automatically setup when a tenant is created. Since Tempest needs isolated tenants to function properly it also needs to handle network allocation. By default the base test class will allocate a network, subnet, and router automatically (this depends on the configured credential provider, for more details see: Network Creation/Usage for Servers). However, there are situations where you do no need all of these resources allocated (or your TestCase inherits from a class that overrides the default in tempest/test.py). There is a class level mechanism to override this allocation and specify which resources you need. To do this you need to call cls.set_network_resources() in the setup_credentials() method before the super(). For example:
from tempest import test class TestExampleCase(test.BaseTestCase): @classmethod def setup_credentials(cls): cls.set_network_resources(network=True, subnet=True, router=False) super(TestExampleCase, cls).setup_credentials()
There are 2 quirks with the usage here. First for the set_network_resources function to work properly it must be called before super(). This is so that children classes’ settings are always used instead of a parent classes’. The other quirk here is that if you do not want to allocate any network resources for your test class simply call set_network_resources() without any arguments. For example:
from tempest import test class TestExampleCase(test.BaseTestCase): @classmethod def setup_credentials(cls): cls.set_network_resources() super(TestExampleCase, cls).setup_credentials()
This will not allocate any networking resources. This is because by default all the arguments default to False.
It’s also worth pointing out that it is common for base test classes for different services (and scenario tests) to override this setting. When inheriting from classes other than the base TestCase in tempest/test.py it is worth checking the immediate parent for what is set to determine if your class needs to override that setting.
Running some tests in serial¶
Tempest potentially runs test cases in parallel, depending on the configuration. However, sometimes you need to make sure that tests are not interfering with each other via OpenStack resources. Tempest creates separate projects for each test class to separate project based resources between test cases.
If your tests use resources outside of projects, e.g. host aggregates then
you might need to explicitly separate interfering test cases. If you only need
to separate a small set of testcases from each other then you can use the
However, in some cases a small set of tests needs to be run independently from
the rest of the test cases. For example, some of the host aggregate and
availability zone testing needs compute nodes without any running nova server
to be able to move compute hosts between availability zones. But many tempest
tests start one or more nova servers. In this scenario you can mark the small
set of tests that needs to be independent from the rest with the
class decorator. This will make sure that even if tempest is configured to run
the tests in parallel the tests in the marked test class will always be executed
separately from the rest of the test cases.
Please note that due to test ordering optimization reasons test cases marked
@serial execution need to be put under
directory. This will ensure that the serial tests will block the parallel tests
in the least amount of time.
Interacting with Credentials and Clients¶
Once you have your basic TestCase setup you’ll want to start writing tests. To do that you need to interact with an OpenStack deployment. This section will cover how credentials and clients are used inside of Tempest tests.
The primary interface with which you interact with both credentials and API clients is the client manager object. These objects are created automatically by the base test class as part of credential setup (for more details see the previous Allocating Credentials section). Each manager object is initialized with a set of credentials and has each client object already setup to use that set of credentials for making all the API requests. Each client is accessible as a top level attribute on the manager object. So to start making API requests you just access the client’s method for making that call and the credentials are already setup for you. For example if you wanted to make an API call to create a server in Nova:
from tempest import test class TestExampleCase(test.BaseTestCase): def test_example_create_server(self): self.os_primary.servers_client.create_server(...)
is all you need to do. As described previously, in the above example the
self.os_primary is created automatically because the base test class sets the
credentials attribute to allocate a primary credential set and initializes
the client manager as
self.os_primary. This same access pattern can be used
for all of the clients in Tempest.
In certain cases you need direct access to the credentials (the most common
use case would be an API request that takes a user or project id in the request
body). If you’re in a situation where you need to access this you’ll need to
credentials object which is allocated from the configured
credential provider in the base test class. This is accessible from the manager
object via the manager’s
credentials attribute. For example:
from tempest import test class TestExampleCase(test.BaseTestCase): def test_example_create_server(self): credentials = self.os_primary.credentials
The credentials object provides access to all of the credential information you would need to make API requests. For example, building off the previous example:
from tempest import test class TestExampleCase(test.BaseTestCase): def test_example_create_server(self): credentials = self.os_primary.credentials username = credentials.username user_id = credentials.user_id password = credentials.password tenant_id = credentials.tenant_id