tempest/doc/source/write_tests.rst

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 it's role as an integration test suite running against a real cloud.

Note

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_plugin 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:

1. setUpClass
2. setUp
3. Test Execution
4. tearDown
5. doCleanups
6. tearDownClass

setUpClass

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:

• skip_checks
• setup_credentials
• setup_clients
• resource_setup

which is executed in that order. An example of a TestCase which defines all of these would be:

from tempest import config
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.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(...)

Allocating Credentials

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 tempest_cred_provider_conf 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 cls.os and cls.os_adm 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 cls.os_roles_operator and cls.os_roles_operator_alt respectively.

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:

Credentials Entry	Manager Variable
primary	cls.os
admin	cls.os_adm
alt	cls.os_alt
[$label, $role]	cls.os_roles$label

By default cls.os 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: tempest_conf_network_allocation) 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.

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.

Manager Objects

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 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.servers_client.create_server(...)

is all you need to do. As described previously, in the above example the self.os 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. This same access pattern can be used for all of the clients in Tempest.

Credentials Objects

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 access the 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.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.credentials
    username = credentials.username
    user_id = credentials.user_id
    password = credentials.password
    tenant_id = credentials.tenant_id