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Flutter devicelab
"Devicelab" (a.k.a. "cocoon") is a physical lab that tests Flutter on real Android and iOS devices.
This package contains the code for test framework and the tests. More generally the tests are referred to as "tasks" in the API, but since we primarily use it for testing, this document refers to them as "tests".
Build results are available at https://flutter-dashboard.appspot.com.
Reading the dashboard
The build page
The build page is accessible at https://flutter-dashboard.appspot.com/build.html. This page reports the health of build servers, called agents, and the statuses of build tasks.
Agents
A green agent is considered healthy and ready to receive new tasks to build. A red agent is broken and does not receive new tasks.
In the example below, the dashboard shows that the linux2
agent is broken and
requires attention. All other agents are healthy.
Tasks
The table below the agent statuses displays the statuses of build tasks. Task statuses are color-coded. The following statuses are available:
New task (light blue): the task is waiting for an agent to pick it up and start the build.
Task is running (spinning blue): an agent is currently building the task.
Task succeeded (green): an agent reported a successful completion of the task.
Task is flaky (yellow): the task was attempted multiple time, but only the latest attempt succeeded (we currently only try twice).
Task failed (red): the task failed all of the attempts.
Task underperformed (orange): currently not used.
Task was skipped (transparent): the task is not scheduled for a build. This
usually happens when a task is removed from manifest.yaml
file.
Task status unknown (purple): currently not used.
In addition to color-coding, a task may display a question mark. This means that the task was marked as flaky manually. The status of such task is ignored when considering whether the build is broken or not. For example, if a flaky task fails, GitHub will not prevent PR submissions. However, if the latest status of a non-flaky task is red, all pending PRs will contain a warning about the broken build and recommend caution when submitting.
Legend:
The example below shows that commit e122d5d
caused a wide-spread breakage,
which was fixed by bdc6f10
. It also shows that Cirrus and Chrome
Infra (left-most tasks) decided to skip building these commits. Hovering over
a cell will pop up a tooltip containing the name of the broken task. Clicking
on the cell will open the log file in a new browser tab (only visible to core
contributors as of today).
Why is a task stuck on "new task" status?
The dashboard aggregates build results from multiple build environments,
including Cirrus, Chrome Infra, and devicelab. While devicelab
tests every commit that goes into the master
branch, other environments
may skip some commits. For example, Cirrus will only test the
last commit of a PR that's merged into the master
branch. Chrome Infra may
skip commits when they come in too fast.
How the devicelab runs the tasks
The devicelab agents have a small script installed on them that continuously asks the CI server for tasks to run. When the server finds a suitable task for an agent it reserves that task for the agent. If the task succeeds, the agent reports the success to the server and the dashboard shows that task in green. If the task fails, the agent reports the failure to the server, the server increments the counter counting the number of attempts it took to run the task and puts the task back in the pool of available tasks. If a task does not succeed after a certain number of attempts (as of this writing the limit is 2), the task is marked as failed and is displayed using red color on the dashboard.
Running tests locally
Do make sure your tests pass locally before deploying to the CI environment. Below is a handful of commands that run tests in a similar way to how the CI environment runs them. These commands are also useful when you need to reproduce a CI test failure locally.
Prerequisites
You must set the ANDROID_HOME
or ANDROID_SDK_ROOT
environment variable to run
tests on Android. If you have a local build of the Flutter engine, then you have
a copy of the Android SDK at .../engine/src/third_party/android_tools/sdk
.
You can find where your Android SDK is using flutter doctor
.
Warnings
Running devicelab will do things to your environment.
Notably, it will start and stop gradle, for instance.
Running all tests
To run all tests defined in manifest.yaml
, use option -a
(--all
):
../../bin/cache/dart-sdk/bin/dart bin/run.dart -a
Running specific tests
To run a test, use option -t
(--task
):
# from the .../flutter/dev/devicelab directory
../../bin/cache/dart-sdk/bin/dart bin/run.dart -t {NAME_OR_PATH_OF_TEST}
Where NAME_OR_PATH_OF_TEST
can be either of:
- the name of a task, which you can find in the
manifest.yaml
file in this directory. Example:complex_layout__start_up
. - the path to a Dart file corresponding to a task, which resides in
bin/tasks
. Tip: most shells support path auto-completion using the Tab key. Example:bin/tasks/complex_layout__start_up.dart
.
To run multiple tests, repeat option -t
(--task
) multiple times:
../../bin/cache/dart-sdk/bin/dart bin/run.dart -t test1 -t test2 -t test3
To run tests from a specific stage, use option -s
(--stage
).
Currently there are only three stages defined, devicelab
,
devicelab_ios
and devicelab_win
.
../../bin/cache/dart-sdk/bin/dart bin/run.dart -s {NAME_OF_STAGE}
Running tests against a local engine build
To run device lab tests against a local engine build, pass the appropriate
flags to bin/run.dart
:
../../bin/cache/dart-sdk/bin/dart bin/run.dart --task=[some_task] \
--local-engine-src-path=[path_to_local]/engine/src \
--local-engine=[local_engine_architecture]
An example of of a local engine architecture is android_debug_unopt_x86
.
Reproducing broken builds locally
To reproduce the breakage locally git checkout
the corresponding Flutter
revision. Note the name of the test that failed. In the example above the
failing test is flutter_gallery__transition_perf
. This name can be passed to
the run.dart
command. For example:
../../bin/cache/dart-sdk/bin/dart bin/run.dart -t flutter_gallery__transition_perf
Writing tests
A test is a simple Dart program that lives under bin/tests
and uses
package:flutter_devicelab/framework/framework.dart
to define and run a task.
Example:
import 'dart:async';
import 'package:flutter_devicelab/framework/framework.dart';
Future<void> main() async {
await task(() async {
... do something interesting ...
// Aggregate results into a JSONable Map structure.
Map<String, dynamic> testResults = ...;
// Report success.
return new TaskResult.success(testResults);
// Or you can also report a failure.
return new TaskResult.failure('Something went wrong!');
});
}
Only one task
is permitted per program. However, that task can run any number
of tests internally. A task has a name. It succeeds and fails independently of
other tasks, and is reported to the dashboard independently of other tasks.
A task runs in its own standalone Dart VM and reports results via Dart VM service protocol. This ensures that tasks do not interfere with each other and lets the CI system time out and clean up tasks that get stuck.
Adding tests to the CI environment
The manifest.yaml
file describes a subset of tests we run in the CI. To add
your test edit manifest.yaml
and add the following in the "tasks" dictionary:
{NAME_OF_TEST}:
description: {DESCRIPTION}
stage: {STAGE}
required_agent_capabilities: {CAPABILITIES}
Where:
{NAME_OF_TEST}
is the name of your test that also matches the name of the file inbin/tests
without the.dart
extension.{DESCRIPTION}
is the plain English description of your test that helps others understand what this test is testing.{STAGE}
isdevicelab
if you want to run on Android, ordevicelab_ios
if you want to run on iOS.{CAPABILITIES}
is an array that lists the capabilities required of the test agent (the computer that runs the test) to run your test. Available capabilities are:has-android-device
,has-ios-device
.