Running Flutter integration tests in Docker

Prerequisite

• Linux OS
• Installing:
  • Flutter
  • Docker
  • Docker compose
  • KVM https://help.ubuntu.com/community/KVM/Installation

Technologies

• Flutter:

  • Google’s SDK for crafting beautiful, fast user experiences for mobile, web, and desktop from a single codebase. Flutter works with existing code, is used by developers and organizations around the world, and is free and open source.
  • https://github.com/flutter/flutter

• Docker:

  • An open platform for developing, shipping, and running applications
  • https://docs.docker.com/get-started/overview/

• Android Emulator container:

  • Allowing you to find and run the right version of the Emulator without the headache of dependency management, which makes it easy to scale automated tests as part of a CI/CD system without the upkeep cost of a physical device farm
  • https://github.com/google/android-emulator-container-scripts

Why we use Docker to run automation tests

• Scaling tests:

  • Docker provides the ability to package and run an application in a loosely isolated environment, so we can run multiple e2e tests parallel.

• Reusing:

  • Our Dockerfile file and docker-compose.yml file is simple because of reusing container from the community.

• Consistency:

  • Allowing developers to work in standardized environments using local containers which provide applications and services

• Responsive:

  • Docker containers can run on a developer’s local laptop and on cloud providers.

Explanation

• We create Dockerfile for the flutter-app service because we need to copy our source code to the container to build then run tests

FROM cirrusci/flutter:2.8.1

RUN sdkmanager "build-tools;29.0.2"

RUN flutter precache --android --no-web --no-ios --no-universal

COPY pubspec.* .

RUN --mount=type=cache,sharing=locked,target=/flutter flutter pub get

WORKDIR /project

COPY . .

• To run the Flutter integration test we need a process for Android Emulator and a process for Flutter drive. That is why we have 2 services: flutter-app and android-emulator in docker-compose.yml file.

version: "3.9"
services:
  android-emulator:
    image: us-docker.pkg.dev/android-emulator-268719/images/30-google-x64:30.1.2
    devices:
      - /dev/kvm

  flutter-app:
    depends_on:
      - android-emulator
    build: .
    command: make run-test

• But flutter-app and android-emulator are 2 separate services. It means they are not the same network, so we need to connect flutter-app to android-emulator by the following command: adb connect android-emulator:5555. Reference: https://developer.android.com/studio/command-line/adb#wireless

• After flutter-app connected to android-emulator, we can run the Flutter integration tests with flutter drive command. We combine connect emulator script and flutter drive script in run-test command in Makefile.

run-test:
	sleep 10
	adb connect android-emulator:5555
	adb wait-for-device
	bash waiting-for-boot.sh
	flutter pub get
	flutter drive --target test_driver/app.dart

Run the example

• Cloning the source code on Github: https://github.com/phamnhuvu-dev/flutter_android_docker
• After cloning the source code, move to the root of the source code.
• Run make run-docker-test
• If you see the following log after running the above command. You succeeded.

All tests passed!

Summary:

• Using docker for automation tests is being used widely in the software industry, not only Mobile field.
• With Docker’s ability, scaling tests is far easier and faster, helping us to detect breakings and bugs quickly to fix and maintain.
• Maybe you have the same question as almost all mobile developers who’re using macOS to work. How can we run the automation tests on macOS before shipping the source code to the cloud?
  1. We can’t run android-emulator x64 container on macOS because the macOS doesn’t have KVM.
  2. Actually, we can run android-emulator arm with -no-accel but the performance is very bad => can’t use on Intel chip macOS
  3. Running android-emulator arm on ARM chip macOS:
     • Google is working on that: https://github.com/google/android-emulator-container-scripts/issues/211
     • Self-building android-emulator arm image https://github.com/google/android-emulator-container-scripts. I am using Intel macOS so I don’t have ARM macOS to do this. I am waiting for the next M1X Mac mini with 32GB ram, 16GB ram is not enough for me for something paralleling and scaling.
  4. Connecting flutter-app service from container to Android Emulator on macOS, yes we can do that I will write a blog for this.