Testing#
Imagine you’re making a change to the library.
If your change touches Python code, it should probably include at least one test.
What kind of tests should I write?#
We use heuristics to decide when and what sort of tests to write. For example, a pull request implementing a new feature should include enough unit tests to cover the feature’s “happy path” use cases in addition to any known likely edge cases. If the feature involves a new form of communication with another component (like the Datadog Agent or libddwaf), it should probably include at least one integration test exercising the end-to-end communication.
If a pull request fixes a bug, it should include a test that, on the trunk branch, would replicate the bug. Seeing this test pass on the fix branch gives us confidence that the bug was actually fixed.
Where do I put my tests?#
Put your code’s tests in the appropriate subdirectory of the tests
directory based on what they are testing.
If your feature is substantially new, you may decide to create a new tests
subdirectory in the interest
of code organization.
How do I run the test suite?#
We assume you have docker installed.
In addition, you will need riot and hatch.
$ pip install riot==0.19.0
$ pip install hatch~=1.8.0 hatch-containers==0.7.0
Some of our test environments are managed with Riot, others with Hatch.
For riot environments, you can run:
$ scripts/ddtest riot run -p 3.10
This command runs the entire test suite, which is probably not what you want to do.
For hatch environments, you can run:
$ hatch run lint:style
If you make a change to the hatch.toml or library dependencies, be sure to remove environments before re-running:
$ hatch env remove <ENV> # or hatch env prune
How do I run only the tests I care about?#
Note the names of the tests you care about - these are the “test names”.
Find the
Venv
in the riotfile whosecommand
contains the tests you’re interested in. Note theVenv
’sname
- this is the “suite name”.Find the directive in the CI config whose
pattern
is equal to the suite name. Note thedocker_services
section of the directive, if present - these are the “suite services”.Start the suite services, if applicable, with
$ docker-compose up -d service1 service2
.Start the test-runner Docker container with
$ scripts/ddtest
.In the test-runner shell, run the tests with
$ riot -v run --pass-env -p 3.10 <suite_name> -- -s -vv -k 'test_name1 or test_name2'
.
Anatomy of a Riot Command#
$ riot -v run --pass-env -s -p 3.10 <suite_name> -- -s -vv -k 'test_name1 or test_name2'
-v
: Print verbose output--pass-env
: Pass all environment variables in the current shell to the pytest invocation-s
: Skips base install. Ensure you have already generated the base virtual environment(s) before using this flag.-p 3.10
: Run the tests using Python 3.10. You can change the version string if you want.<suite_name>
: A regex matching the names of the RiotVenv
instances to run--
: Everything after this gets treated as apytest
argument-s
: Make potential uses ofpdb
work properly-vv
: Be loud about which tests are being run-k 'test1 or test2'
: Test selection by keyword expression
Why are my tests failing with 404 errors?#
If your test relies on the testagent
service, you might see it fail with a 404 error.
To fix this:
# outside of the testrunner shell
$ docker-compose up -d testagent
# inside the testrunner shell, started with scripts/ddtest
$ DD_AGENT_PORT=9126 riot -v run --pass-env ...
Why is my CI run failing with a message about requirements files?#
.riot/requirements
contains requirements files generated with pip-compile
for every environment specified
by riotfile.py
. Riot uses these files to build its environments, and they do not get rebuilt automatically
when the riotfile changes. Thus, if you make changes to the riotfile, you need to rebuild them.
$ scripts/ddtest scripts/compile-and-prune-test-requirements
You can commit and pull request the resulting changes to files in .riot/requirements
alongside the
changes you made to riotfile.py
.
How do I add a new test suite?#
We use riot, a Python virtual environment constructor, to run the test suites.
It is necessary to create a new Venv
instance in riotfile.py
if it does not exist already. It can look like this:
Venv(
name="asyncio",
command="pytest {cmdargs} tests/contrib/asyncio",
pys=select_pys(),
pkgs={
"pytest-asyncio": latest,
},
env={
"DD_ENV_VARIABLE": "1", # if needed
},
)
Once a Venv
instance has been created, you will be able to run it as explained in the section below.
Next, we will need to add a new CircleCI job to run the newly added test suite at .circleci/config.templ.yml
just like:
asyncio:
<<: *contrib_job
steps:
- run_test:
pattern: 'asyncio'
After this, a new component must be added to tests/.suitespec.json
under "components":
like:
"asyncio": [
"ddtrace/contrib/asyncio/*"
],
Lastly, we will register it as a suite in the same file under "suites":
:
"asyncio": [
"@asyncio",
"tests/contrib/asyncio/*"
],
Once you’ve completed these steps, CircleCI will run the new test suite.
How do I update a Riot environment to use the latest version of a package?#
Reading through the above example and others in riotfile.py
, you may notice that some package versions are specified
as the variable latest
. When the Riotfile is compiled into the .txt
files in the .riot
directory, latest
tells
the compiler to pin the newest version of the package available on PyPI according to semantic versioning.
Because this version resolution happens during Riotfile compilation, latest
doesn’t always mean “latest” once the compiled
requirements files are checked into source control. In order to stay current, these requirements files need to be recompiled
periodically.
Assume you have a Venv
instance in the Riotfile that uses the latest
variable. Note the name
field of this
environment object.
Run
scripts/ddtest
to enter a shell in the testrunner containerexport VENV_NAME=<name_you_noted_above>
Delete all of the requirements lockfiles for the chosen environment, then regenerate them:
for h in `riot list --hash-only "^${VENV_NAME}$"`; do rm .riot/requirements/${h}.txt; done; scripts/compile-and-prune-test-requirements
Commit the resulting changes to the
.riot
directory, and open a pull request against the trunk branch.