Extension Testing

This guide covers a practical part of testing extensions. Both for extensions developed in kit repo and outside.

Kit Sdk includes omni.kit.test extension and set of build scripts (in premake5-public.lua file) to run extension tests.

Currently, only python tests are supported. You still can test C++ code, but test entry points start from python. It is possible to add support for native C++ testing framework in the future.

Adding Extension Test: Build Scripts

If your extension’s premake5.lua file defines extension project in usual way:

local ext = get_current_extension_info()
project_ext (ext)

It should already have corresponding bat/sh files generated in _build folder, e.g.: _build\windows-x86_64\release\tests-[extension_name].bat

Even if you haven’t written any actual tests, it is already useful. It is a startup/shutdown test, that verifies that all extension dependencies are correct, python imports are working, and that it can start and exit without any errors.

Empty extension test is an already important one. Wrong or missing dependencies is a source of many future issues. Extensions are often developed in the context of certain apps and have implicit expectations. When used in other apps they doesn’t work. Or when extension load order randomly changes and other extensions you implicitly depend on start to load after you.

How does it work?

You can look inside Kit’s premake5-public.lua file to find details on how it happens, follow the function project_ext(ext, args).

If you look inside that shell script, it basically runs empty Kit + omni.kit.test + passes your extension. That will run test system process which in turn will run another, tested process, which is basically: empty Kit + omni.kit.test + --enable [your extension].

test system process prints each command it uses to spawn a new process. You can copy that command and use exactly the same command for debugging purposes.

You may ask why we spawn a process, which spawns another process? And both have omni.kit.test? Many reasons:

  1. Test system process monitors tested process:

    • It can kill it in case of timeout.

    • Reads return code. If != 0 indicates test failure.

    • Reads stdout/stderr for error messages.

  2. Test system process reads extension.toml of tested extension in advance. That allows us to specify test settings, cmd args, etc.

  3. It can run many extension tests in parallel.

  4. It can download extensions from the registry before testing.

omni.kit.test has separate modules for both test system process (exttests.py) and tested process (unittests.py).

Writing First Test

Tested process runs with omni.kit.test which has unittests module. It is a wrapper on top of python’s standard unittest framework.

It adds support for async/await usage in tests. Allowing test method to be async and run for many updates/frames. For instance test can at any point call await omni.kit.app.get_app().next_update_async() and thus yield test code execution until next update.

All the methods in std unittest can be used (like self.assertEqual etc).

If your extension for instance has:

name = "omni.foo"

Your tests must go into omni.foo.tests module. The testing framework will try to import tests submodule for every python module, it has few benefits:

  1. It only gets imported in test run. Thus it can use test only dependencies or run more expensive code. No need to depend on omni.kit.test everywhere.

  2. It gets imported after other python modules. This way public modules can be imported and used in tests as if tests are written externally (but still inside of an extension). Public API can be tested this way.

An actual test code can look like this:

#   omni.kit.test - std python's unittest module with additional wrapping to add suport for async/await tests
#   For most things refer to unittest docs: https://docs.python.org/3/library/unittest.html
import omni.kit.test

# Import extension python module we are testing with absolute import path, as if we are external user (other extension)
import example.python_ext

# Having a test class dervived from omni.kit.test.AsyncTestCase declared on the root of module will make it auto-discoverable by omni.kit.test
class Test(omni.kit.test.AsyncTestCase):
    # Before running each test
    async def setUp(self):

    # After running each test
    async def tearDown(self):

    # Actual test, notice it is "async" function, so "await" can be used if needed
    async def test_hello_public_function(self):
        result = example.python_ext.some_public_function(4)
        self.assertEqual(result, 256)

All the concepts here are from the standard unittest framework. Test methods start with test_. You need to inherit a base test class, which will be created, setUp() will be called before each test, tearDown() after. Everything can be async or “sync”.

Test Settings

Test Settings: Basics

[[test]] section of extension.toml allows to control how a test process is run. We aim to make that configuration empty and defaults to be reasonable. We also strive to make tests run as close as possible to real usage run. Making test environment the same as production.

However, you can specify which errors to ignore, what additional dependencies to bring, change timeout, pass extra args etc. All the details are in Kit’s Extensions doc.

Below is an example, it shows how to:

  • add extra arguments

  • add test only dependencies (extensions)

  • change timeout

  • include and exclude error messages from failing tests

  args = ["--/some/setting=1"]
  dependencies = ["omni.kit.capture"]
  timeout = 666
  stdoutFailPatterns.include = ["*[error]*", "*[fatal]*"]
  stdoutFailPatterns.exclude = [
    "*Leaking graphics objects*",  # Exclude graphics leaks until fixed

Test Settings: Where to look for python tests?

By default test system process (exttests.py) reads all [[python.module]] entries from the tested extension and searches for tests in each of them. You can override it by explicitly setting where to look for tests:

pythonTests.include = ["omni.foo.*"]
pythonTests.exclude = ["omni.foo.bar.*"]

This is useful if you want to bring tests from other extensions. Especially, when testing apps.

Test Settings: Multiple test processes

Each [[test]] entry is a new process. Thus by default, each extension will run one test process to run all python tests that extension has.

When adding multiple entries they must be named to distinguish them (in artifacts, logs, etc):

name = "basic"
pythonTests.include = [ "omni.foo.*basic*" ]

name = "other"
pythonTests.include = [ "omni.foo.*other*" ]

To select which process to run: pass -n [wildcard]", where [wildcard] is a name. * are supported:

> _build\windows-x86_64\release\tests-example.python_ext.bat -n other

Running Your Test

To run test just call shell script described above: _build\windows-x86_64\release\tests-[extension_name].bat.

Run subset of tests

Pass -f [wildcard]", where [wildcard] is a name of the test or part of the name. * are supported:

> _build\windows-x86_64\release\tests-example.python_ext.bat -f "public_function"

Developing Tests

Pass --dev or --/exts/omni.kit.test/testExtUIMode=1. That will start a window with a list of tests instead of immediately running them. Here you can select tests to run. Change code, extension hotreloads, run again. E.g.:

> _build\windows-x86_64\release\tests-example.python_ext.bat --dev"

Note that this test run environment is a bit different. Extra extensions required to render basic UI are enabled.

Disabling a python test

Use decorators from unittest module, e.g.:

    @unittest.skip("Fails on linux now, to be fixed")  # OM-12345
    async def test_create_delete(self):

Pass extra cmd args to the test

If you want to pass extra arguments for debugging purposes (for permanent use [[test]] config part) you can pass --/exts/omni.kit.test/testExtArgs/0="-v". It is an array setting, so notice /0 syntax.

Choose an app to run tests in

All tests run in a context of an app, which by default is empty app: "${kit}/apps/omni.app.test_ext.kit". You can instead pass your own kit file, where you can define any extra settings.

In this kit file you can change testing environment, enable some debug settings or extensions. omni.app.test_ext.kit app kit comes with a few useful settings commented.

Python debugger

To enable python debugger you can use omni.kit.debug.python extension. One way is to uncomment in omni.app.test_ext.kit:

    # "omni.kit.debug.python" = {}

You can use VSCode to attach python debugger. Look into omni.kit.debug.python extension.toml for more settings.

Wait for the debugger to attach

If you want to attach a debugger you can run with -d. When Kit runs with -d it stops and wait for debugger to attach, that also can be skipped. Since we run 2 process and you likely want to attach to second one - skip the first one. E.g.:

λ _build\windows-x86_64\release\tests-example.python_ext.bat -d
[omni.kit.app] Waiting for debugger to attach, press any key to skip... [pid: 19052]
[Info] [carb] Logging to file: C:/projects/extensions/kit-template/_build/windows-x86_64/release//logs/Kit/kit/103.0/kit_20211018_160436.log
Test output path: C:\projects\extensions\kit-template\_testoutput
Running 1 Extension Test(s).

||||||||||||||||||||||||||||||  [EXTENSION TEST START: example.python_ext-0.2.1]  ||||||||||||||||||||||||||||||
>>> running process: C:\projects\extensions\kit-template\_build\windows-x86_64\release\kit\kit.exe ${kit}/apps/omni.app.test_ext.kit --enable example.python_ext-0.2.1 --/log/flushStandardStreamOutput=1 --/app/name=exttest_example.python_ext-0.2.1 --/log/file='C:\projects\extensions\kit-template\_testoutput/exttest_example.python_ext-0.2.1/exttest_example.python_ext-0.2.1_2021-10-18T16-04-37.log' --/crashreporter/dumpDir='C:\projects\extensions\kit-template\_testoutput/exttest_example.python_ext-0.2.1' --/plugins/carb.profiler-cpu.plugin/saveProfile=1 --/plugins/carb.profiler-cpu.plugin/compressProfile=1 --/app/profileFromStart=1 --/plugins/carb.profiler-cpu.plugin/filePath='C:\projects\extensions\kit-template\_testoutput/exttest_example.python_ext-0.2.1/ct_exttest_example.python_ext-0.2.1_2021-10-18T16-04-37.gz' --ext-folder c:/projects/extensions/kit-template/_build/windows-x86_64/release/kit/extsPhysics --ext-folder c:/projects/extensions/kit-converters/_build/windows-x86_64/release/exts --ext-folder C:/projects/extensions/kit-template/_build/windows-x86_64/release/exts --ext-folder C:/projects/extensions/kit-template/_build/windows-x86_64/release/apps --enable omni.kit.test --/exts/omni.kit.test/runTestsAndQuit=true --/exts/omni.kit.test/includeTests/0='example.python_ext.*' --portable-root C:\projects\extensions\kit-template\_build\windows-x86_64\release\/ -d
|| [omni.kit.app] Waiting for debugger to attach, press any key to skip... [pid: 22940]

Reading Logs

Each process writes own log file. Paths to those files are printed to stdout. You can run with -v to increase the verbosity of standard output.

Run from Extension Manager

You can also run tests from UI. Run any Kit with UI, for instance omni.app.mini.kit. Go to Extension Manager, find your extension, open Tests tab. Here you can run the same tests.

It will also run a separate process and works exactly the same way as running from the shell script.

Marking tests as flaky/unreliable

It is often the case that certain tests fails randomly, with some probability. That blocks CI/CD pipeline and lowers trust into TC state.

Tickets needs to be created and such tests can be:

  1. Disabled

  2. Marked as unreliable

Unreliable tests will still run, but not fail the pipeline. Add unreliable = true to extension.toml:

unreliable = true

That will make all tests in this extension unreliable. To mark only subset of tests as such they first need to be moved into separate process. Naming convention on a test method name can be used to separate one from another. Example:

pythonTests.exclude = [ "*UNRELIABLE*" ]

unreliable = true
pythonTests.include = [ "omni.foo.*UNRELIABLE*" ]

repo_test: Running All Tests

To run all tests in the repo we use repo_test repo tool. Which is yet another process that runs before anything. It globs all the files according to repo.toml [repo_test] section configuration and runs them.

It is one entry point to run all sort of tests. Different kinds of tests are grouped into suites. By default, it will run one suite, but you can select which one to run with --suite [suite name]. Look at repo.toml for entries like [repo_test.suites.pythontests]. In that example: pythontests is a suite name.

You can also choose build config to run tests one: -c release or -c debug. In kit the default is debug, in other repos: release.

Run all tests in the repo:

> repo.bat test


> repo.bat test --suite pythontests -c release

Just print them:

> repo.bat test -l

To filter tests:

> repo.bat test -f foobar

For more options (as usual):

> repo.bat test -h

Excluding Tests from TC:

You can control which shell scripts to run with repo_test in repo.toml:

# Run all test
include = [
exclude = [
  "tests-example.cpp_ext*", # Exclude some script
args = []

Check before running with:

> repo.bat test -l

omni.kit.ui_test: Writing UI tests

Many extensions build various windows and widgets using omni.ui. The best way to test those is by simulating user interactions with UI. For that omni.kit.ui_test extension can be used.

omni.kit.ui_test provides a way to query UI elements and interact with them. To start add test dependency to this extension:

dependencies = [

Now you can import and use it in tests. Example:

import omni.kit.ui_test as ui_test

async def test_button(self):
    # Find a button
    button = ui_test.find("Nice Window//Frame/**/Button[*]")

    # button is a reference, actual omni.ui.Widget can be accessed:
    print(type(button.widget))  # <class 'omni.ui._ui.Button'>

    # Click on button
    await button.click())

Refer to omni.kit.ui_test documentation for more examples and API.