android_engine_test

This directory contains a sample app and tests that demonstrate how to use the (experimental) native Flutter Driver API to drive Flutter apps that run on Android devices or emulators, interact with and capture screenshots of the app, and compare the screenshots against golden images.

[!CAUTION] This test suite is a very end-to-end suite that is testing a combination of the graphics backend, the Android embedder, the Flutter framework, and Flutter tools, and only useful when the documentation and naming stays up to date and is clearly actionable.

Please take extra care when updating the test suite to also update the README.

How it runs on CI (LUCI)

See dev/bots/suite_runners/run_android_engine_tests.dart, but tl;dr:

# TIP: If golden-files do not exist locally, this command will fail locally.
SHARD=android_engine_vulkan_tests bin/cache/dart-sdk/bin/dart dev/bots/test.dart
SHARD=android_engine_opengles_tests bin/cache/dart-sdk/bin/dart dev/bots/test.dart

Running the apps and tests

Each lib/{prefix}_main.dart file is a standalone Flutter app that you can run on an Android device or emulator.

• flutter_rendered_blue_rectangle
• external_texture/surface_producer_smiley_face
• external_texture/surface_texture_smiley_face
• platform_view/hybrid_composition_platform_view
• platform_view/texture_layer_hybrid_composition_platform_view
• platform_view/virtual_display_platform_view
• platform_view_tap_color_change
• system_ui_mode_transitions

flutter_rendered_blue_rectangle

This app displays a full screen blue rectangle. It mostly serves as a test that Flutter can run at all on the target device, and that the Flutter (native) driver can take a screenshot and compare it to a golden image. If this app or test fails, it's likely none of the other apps or tests will work either.

# Run the app
$ flutter run lib/flutter_rendered_blue_rectangle_main.dart

# Run the test
$ flutter drive lib/flutter_rendered_blue_rectangle_main.dart

external_texture/surface_producer_smiley_face

This app displays a full screen rectangular deformed smiley face with a yellow background. It tests the SurfaceProducer API end-to-end, including historic regression cases around backgrounding the app, trimming memory, and resuming the app.

# Run the app
$ flutter run lib/external_texture/surface_producer_smiley_face_main.dart

# Run the test
$ flutter drive lib/external_texture/surface_producer_smiley_face_main.dart

external_texture/surface_texture_image_smiley_face

This app displays a full screen rectangular deformed smiley face with a yellow background. It tests getImageFromTexture API in dart:ui.

# Run the app
$ flutter run lib/external_texture/surface_texture_image_smiley_face_main.dart

# Run the test
$ flutter drive lib/external_texture/surface_texture_image_smiley_face_main.dart

external_texture/surface_texture_smiley_face

This app displays a full screen rectangular deformed smiley face with a yellow background. It tests the SurfaceTexture API end-to-end.

# Run the app
$ flutter run lib/external_texture/surface_texture_smiley_face_main.dart

# Run the test
$ flutter drive lib/external_texture/surface_texture_smiley_face_main.dart

platform_view/hybrid_composition_platform_view

This app displays a blue orange gradient, the app is backgrounded, and then resumed. It tests the Hybrid Composition implementation.

# Run the app
$ flutter run lib/platform_view/hybrid_composition_platform_view_main.dart

# Run the test
$ flutter drive lib/platform_view/hybrid_composition_platform_view_main.dart

platform_view/texture_layer_hybrid_composition_platform_view

This app displays a blue orange gradient, the app is backgrounded, and then resumed. It tests the Texture Layer Hybrid Composition implementation.

# Run the app
$ flutter run lib/platform_view/texture_layer_hybrid_composition_platform_view_main.dart

# Run the test
$ flutter drive lib/platform_view/texture_layer_hybrid_composition_platform_view_main.dart

platform_view/virtual_display_platform_view

This app displays a blue orange gradient, the app is backgrounded, and then resumed. It tests the Virtual Display implementation.

# Run the app
$ flutter run lib/platform_view/virtual_display_platform_view_main.dart

# Run the test
$ flutter drive lib/platform_view/virtual_display_platform_view_main.dart

platform_view_tap_color_change

This app displays a blue rectangle, using platform views, which upon being tapped (natively, not by Flutter), changes from blue to red.

# Run the app
$ flutter run lib/platform_view_tap_color_change_main.dart

# Run the test
$ flutter drive lib/platform_view_tap_color_change_main_test.dart

system_ui_mode_transitions

This app exposes a Flutter Driver requestData handler that applies SystemUiMode values in sequence and reads the resulting decor-view systemUiVisibility flags via the native_driver method channel. The companion test driver asserts that switching to edgeToEdge from any hiding mode (leanBack/immersive/immersiveSticky) clears FLAG_FULLSCREEN/FLAG_HIDE_NAVIGATION, and that switching from edgeToEdge to a hiding mode applies the expected immersive flags.

The regression-named test reproduces #186723 on the immersiveSticky → edgeToEdge cell. Requires Android 10 (API 29) or later; older API levels skip.

# Run the app
$ flutter run lib/system_ui_mode_transitions_main.dart

# Run the test
$ flutter drive lib/system_ui_mode_transitions_main.dart

Deflaking

Use tool/deflake.dart <path/to/lib/main.dart> to, in 1-command:

• Build an APK.
• Establish a baseline set of golden-files locally.
• Run N tests (by default, 10) in the same state, asserting the same output.

For example:

dart tool/deflake.dart lib/flutter_rendered_blue_rectangle_main.dart

For more options, see dart tool/deflake.dart --help.