docs/contributing/testing.md

# Testing

The testing strategy for Perfetto is rather complex due to the wide variety
of build configurations and embedding targets.

Common test targets (all platforms / checkouts):

`perfetto_unittests`:  
Platform-agnostic unit-tests.

`perfetto_integrationtests`:  
End-to-end tests, involving the protobuf-based IPC transport and ftrace
integration (Linux/Android only).

`perfetto_benchmarks`:  
Benchmarks tracking the performance of: (i) trace writing, (ii) trace readback
and (iii) ftrace raw pipe -> protobuf translation.

## Running tests

### On Linux / MacOS

```bash
tools/ninja -C out/default perfetto_{unittests,integrationtests,benchmarks}
out/default/perfetto_unittests --gtest_help
```

`perfetto_integrationtests` requires that the ftrace debugfs directory is
is readable/writable by the current user on Linux:

```bash
sudo chown  -R $USER /sys/kernel/debug/tracing
```

### On Android

1.  Connect a device through `adb`
2.  Start the build-in emulator (supported on Linux and MacOS):

```bash
tools/install-build-deps --android
tools/run_android_emulator &
```

3. Run the tests (either on the emulator or physical device):

```bash
tools/run_android_test out/default perfetto_unittests
```

## Continuous testing

Perfetto is tested in a variety of locations:

**Perfetto CI**: https://ci.perfetto.dev/  
Builds and runs perfetto\_{unittests,integrationtests,benchmarks} from the
standalone checkout. Benchmarks are ran in a reduced form for smoke testing.
See [this doc](/docs/design-docs/continuous-integration.md) for more details.

**Android CI** (see go/apct and go/apct-guide):  
runs only `perfetto_integrationtests`

**Android presubmits (TreeHugger)**:  
Runs before submission of every AOSP CL of `external/perfetto`.

**Android CTS** (Android test suite used run to ensure API compatibility):  
Rolling runs internally.

Note that Perfetto CI uses the standalone build system and the others build as
part of the Android tree.

## Unit tests

Unit tests exist for most of the code in Perfetto on the class level. They
ensure that each class broadly works as expected.

Unit tests are currently ran on ci.perfetto.dev and build.chromium.org.
Running unit tests on APCT and Treehugger is WIP.

## Integration tests

Integration tests ensure that subsystems (importantly ftrace and the IPC layer)
and Perfetto as a whole is working correctly end-to-end.

There are two configurations in which integration tests can be run:

**1. Production mode** (Android-only)  
This mode assumes that both the tracing service (`traced`) and the OS probes
service (`traced_probes`) are already running. In this mode the test enables
only the consumer endpoint and tests the interaction with the production
services. This is the way our Android CTS and APCT tests work.

**2. Standalone mode**:  
Starting up the daemons in the test itself and then testing against them.
This is how standalone builds are tested. This is the only supported way to
run integration tests on Linux and MacOS.

## Trace Processor diff tests

Trace Processor is mainly tested using so called "diff tests" rather than
unit tests. Unit tests have proven too brittle when dealing with code that
parses traces — they require painful mechanical updates whenever the
parsing logic is refactored — so they are reserved for the low-level
building blocks the rest of Trace Processor is built on. Everything else
(parsing events, table schemas, stdlib modules, dynamic tables) is covered
by diff tests.

For these tests, Trace Processor parses a known trace and executes a query
string or file. The output of these queries is then compared (i.e. "diff"ed)
against an expected output file and discrepancies are highlighted.

Similar diff tests are also available when writing metrics — instead of a
query, the metric name is used and the expected output string contains
the expected result of computing the metric.

These tests (for both queries and metrics) can be run as follows:

```bash
tools/ninja -C <out directory>
tools/diff_test_trace_processor.py <out directory>/trace_processor_shell
```

TIP: Query diff tests are expected to only have a single query which produces
output in the whole file (usually at the end). Calling
`SELECT RUN_METRIC('metric file')` can trip up this check as this query
generates some hidden output. To address this issue, if a query only has
column is named `suppress_query_output`, even if it has output, this will
be ignored (for example,
`SELECT RUN_METRIC('metric file') as suppress_query_output`)

### Adding a new diff test

All diff tests live under [`test/trace_processor`](/test/trace_processor) in
`tests{_category_name}.py` files as methods of a class. To add a new test,
add a new method starting with `test_` in the suitable Python file.

Methods cannot take arguments and have to return a `DiffTestBlueprint`:

```python
class DiffTestBlueprint:
  trace: Union[Path, Json, Systrace, TextProto]
  query: Union[str, Path, Metric]
  out: Union[Path, Json, Csv, TextProto]
```

_Trace_ and _Out_: For every type apart from `Path`, contents of the object
will be treated as file contents so it has to follow the same rules.

_Query_: For metric tests it is enough to provide the metric name. For query
tests there can be a raw SQL statement, for example `"SELECT * FROM SLICE"`,
or a path to an `.sql` file.

NOTE: `trace_processor_shell` and the associated proto descriptors need to
be built before running `tools/diff_test_trace_processor.py`. The easiest
way to do this is to run `tools/ninja -C <out directory>` both initially
and on every change to Trace Processor code.

#### Choosing where to add diff tests

`diff_tests/` contains directories corresponding to different areas of
Trace Processor:

1. **stdlib**: Tests focusing on the PerfettoSQL Standard Library, both the
   prelude and the regular modules. The subdirectories generally correspond
   to directories in `perfetto_sql/stdlib`.
2. **parser**: Tests focusing on ensuring different trace formats are
   parsed correctly and the corresponding built-in tables are populated.
3. **syntax**: Tests focusing on the core syntax of PerfettoSQL (e.g.
   `CREATE PERFETTO TABLE`, `CREATE PERFETTO FUNCTION`).

**Scenario**: A new stdlib module `foo/bar.sql` is being added.

_Answer_: Add the test to `stdlib/foo/bar_tests.py`.

**Scenario**: A new event is being parsed and the focus of the test is to
ensure the event is parsed correctly.

_Answer_: Add the test in one of the `parser` subdirectories. Prefer
adding the test to an existing related directory (e.g. `sched`, `power`)
if one exists.

**Scenario**: A new dynamic table is being added and the focus of the test
is to ensure the dynamic table is correctly computed.

_Answer_: Add the test to `stdlib/dynamic_tables`.

**Scenario**: The internals of Trace Processor are being modified and the
test is to ensure Trace Processor is correctly filtering/sorting important
built-in tables.

_Answer_: Add the test to `parser/core_tables`.

## UI pixel diff tests

The pixel tests are used to ensure core user journeys work by verifying they
are the same pixel to pixel against a golden screenshot. They use a headless
chrome to load the webpage and take a screenshot and compare pixel by pixel a
golden screenshot. You can run these tests by using `ui/run-integrationtests`.

These test fail when a certain number of pixels are different. If these tests
fail, you'll need to investigate the diff and determine if its intentional. If
its a desired change you will need to update the screenshots on a linux machine
to get the CI to pass. You can update them by generating and uploading a new
baseline (this requires access to a google bucket through gcloud which only
googlers have access to, googlers can install gcloud
[here](https://g3doc.corp.google.com/cloud/sdk/g3doc/index.md#installing-and-using-the-cloud-sdk)).

The tests are run in a docker container by default, unless -`-no-docker` is
passed. It's recommended to use the container for a stable and reproducable
testing environment, especially for rebaselining, otherwise it's very likely the
screenshots will not match when run on the CI.

```
ui/run-integrationtests --rebaseline
tools/test_data upload
```

Once finished you can commit and upload as part of your CL to cause the CI to
use your new screenshots.

NOTE: If you see a failing diff test you can see the pixel differences on the CI
by using a link ending with `ui-test-artifacts/index.html`. Report located on
that page contains changed screenshots as well as a command to accept the
changes if these are desirable.

## Android CTS tests

CTS tests ensure that any vendors who modify Android remain compliant with the
platform API.

These tests include a subset of the integration tests above as well as adding
more complex tests which ensure interaction between platform (e.g. Android apps
etc.) and Perfetto is not broken.

The relevant targets are `CtsPerfettoProducerApp` and `CtsPerfettoTestCases`. Once these are built, the following commands should be run:

```bash
adb push $ANDROID_HOST_OUT/cts/android-cts/testcases/CtsPerfettoTestCases64 /data/local/tmp/
adb install -r $ANDROID_HOST_OUT/cts/android-cts/testcases/CtsPerfettoProducerApp.apk
```

Next, the app named `android.perfetto.producer` should be run on the device.

Finally, the following command should be run:

```bash
adb shell /data/local/tmp/CtsPerfettoTestCases64
```

## {#chromium} Chromium waterfall

Perfetto is constantly rolled into chromium's //third_party/perfetto via
[this autoroller](https://autoroll.skia.org/r/perfetto-chromium-autoroll).

The [Chromium CI](https://build.chromium.org) runs the `perfetto_unittests`
target, as defined in the [buildbot config][chromium_buildbot].

You can also test a pending Perfetto CL against Chromium's CI / TryBots
before submitting it. This can be useful when making trickier API changes or to
test on platforms that the Perfetto CI doesn't cover (e.g. Windows, MacOS),
allowing you to verify the patch before you submit it (and it then eventually
auto-rolls into Chromium).

To do this, first make sure you have uploaded pull request to GitHub.
Next, create a new Chromium CL that modifies Chromium's
`//src/DEPS` file.

If you recently uploaded your change, it may be enough to modify the git commit
hash in the `DEPS` entry for `src/third_party/perfetto`:

```
  'src/third_party/perfetto':
    Var('chromium_git') + '/external/github.com/google/perfetto/' + '@' + '8fe19f55468ee227e99c1a682bd8c0e8f7e5bcdb',
```

Replace the git hash with the commit hash of your most recent patch set.

Alternatively, you can add `hooks` to patch in the pending CL on top of
Chromium's current third_party/perfetto revision. For this, add the following
entries to the `hooks` array in Chromium's `//src/DEPS` file, modifying the
`refs/pull/XXXX/head` to the appropriate values for your pull request.

```
  {
    'name': 'fetch_custom_patch',
    'pattern': '.',
    'action': [ 'git', '-C', 'src/third_party/perfetto/',
                'fetch', 'https://github.com/google/perfetto.git',
                'refs/pull/XXXX/head',
    ],
  },
  {
    'name': 'apply_custom_patch',
    'pattern': '.',
    'action': ['git', '-C', 'src/third_party/perfetto/',
               '-c', 'user.name=Custom Patch', '-c', 'user.email=custompatch@example.com',
               'cherry-pick', 'FETCH_HEAD',
    ],
  },
```

If you'd like to test your change against the SDK build of Chrome, you
can add `Cq-Include-Trybots:` lines for perfetto SDK trybots to the change
description in gerrit (this won't be needed once Chrome's migration to the
SDK is complete, see [tracking bug][sdk_migration_bug]):

```
Cq-Include-Trybots: luci.chromium.try:linux-perfetto-rel
Cq-Include-Trybots: luci.chromium.try:android-perfetto-rel
Cq-Include-Trybots: luci.chromium.try:mac-perfetto-rel
Cq-Include-Trybots: luci.chromium.try:win-perfetto-rel
```

[chromium_buildbot]: https://cs.chromium.org/search/?q=perfetto_.*tests+f:%5Esrc/testing.*json$&sq=package:chromium&type=cs
[chromium_cl]: https://chromium-review.googlesource.com/c/chromium/src/+/2030528
[sdk_migration_bug]: https://crbug.com/1006541