A screenshot image with overlaid status bar placed in a device frame.

For an example of images generated with Screenshots on a live app in both stores see:

See a demo of Screenshots in action:

For introduction to Screenshots see https://medium.com/@nocnoc/automated-screenshots-for-flutter-f78be70cd5fd.

Screenshots

Screenshots is a standalone command line utility and package for capturing screenshot images for Flutter.

Screenshots will start the required android emulators and iOS simulators (or find attached devices), run tests, process the captured screenshots, and drop them off to Fastlane for delivery to both stores.

Screenshots is inspired by three tools from Fastlane:

1. Snapshots
   This is used to capture screenshots on iOS using iOS UI Tests.
2. Screengrab
   This captures screenshots on android using Android Espresso tests.
3. FrameIt
   This is used to place captured iOS screenshots in a device frame.

Since all three of these Fastlane tools do not work with Flutter, Screenshots combines key features of these Fastlane tools into one tool.

Features

Since Flutter integration testing is designed to work transparently across iOS and Android, capturing images using Screenshots is easy.

Features include:

1. Works with existing tests
   Add a single line for each screenshot.
2. Run tests on any device
   Select the devices to run on using a convenient config file. Screenshots will find the devices (real or emulated) and run tests.
3. One run for both platforms
   Screenshots runs tests on both iOS and Android in one run.
   (as opposed to making separate Snapshots and Screengrab runs)
4. One run for multiple locales
   If app supports multiple locales, Screenshots will optionally set the locales listed in the config file before running each test.
5. One run for frames
   Optionally places images in device frames in same run.
   (as opposed to making separate FrameIt runs... which supports iOS only)
6. One run for clean status bars
   Every image that Screenshots generates has a clean status bar.
   (no need to run a separate stage to clean-up status bars)
7. Works with Fastlane
   Screenshots drops-off images where Fastlane expects to find them. Fastlane's deliver and supply can then be used to upload to respective stores.
8. Works with FrameIt
   Works with Fastlane's FrameIt text and background feature to add text, etc... to a framed screenshot generated by screenshots.
9. Works with any attached real devices
   Use any number of real devices to capture screenshots.

Additional automation features:

1. Screenshots runs in the cloud.
   For live demo of Screenshots running with the internationalized example app on macOS, linux and windows in cloud, see below
2. Screenshots works with any CI/CD tool.
   For live demo of uploading images, generated by Screenshots, to both store consoles, see demo of Fledge at https://github.com/mmcc007/fledge#demo

Installation

On macOS:

brew update && brew install imagemagick
pub global activate screenshots

On linux:

# Debian, Ubuntu or Linux Mint
sudo apt-get install imagemagick
# Fedora, CentOS or RHEL
sudo yum install ImageMagick
# OpenSUSE
sudo zypper install imagemagick

pub global activate screenshots

Note: on linux ImageMagick is often already installed.

On windows:

choco install imagemagick.app
pub global activate screenshots

Note: ImageMagick v7 or later is recommended on windows.

If pub is not found, add to PATH using:

On macOS/Linux:

export PATH="<path to flutter installation directory>/bin/cache/dart-sdk/bin:$PATH"

On windows:

set PATH=<path to flutter installation directory>\flutter\bin\cache\dart-sdk\bin;%APPDATA%\Pub\Cache\bin;%PATH%

Note: if running on Windows or Linux, can only run android devices/emulators. To also run on macOS use a CI that supports macOS.

Usage

screenshots

Or, if using a config file other than the default 'screenshots.yaml':

screenshots -c <path to config file>

Other options:

usage: screenshots [-h] [-c <config file>] [-m <normal|recording|comparison|archive>] [-f <flavor>] [-b <true|false>] [-v]

sample usage: screenshots

-c, --config=<screenshots.yaml>                     Path to config file.
                                                    (defaults to "screenshots.yaml")

-m, --mode=<normal|recording|comparison|archive>    If mode is recording, screenshots will be saved for later comparison.
                                                    If mode is comparison, screenshots will be compared with recorded.
                                                    If mode is archive, screenshots will be archived (and cannot be uploaded via fastlane).
                                                    [normal (default), recording, comparison, archive]

-f, --flavor=<flavor name>                          Flavor name.
-b, --build=<true|false>                            Force build and install of app for all devices.
                                                    Override settings in screenshots.yaml (if any).
                                                    [true, false]

-v, --verbose                                       Noisy logging, including all shell commands executed.
-h, --help                                          Display this help information.

Modifying tests for Screenshots

A special function is provided in the Screenshots package that is called by the test to capture a screenshot. Screenshots will then process the images appropriately during a Screenshots run.

To capture screenshots in tests:

1. Add Screenshots package in app's pubspec.yaml's dev_dependencies section

   dev_dependencies:
     screenshots: ^<current version>

2. In tests
   1. Import the dependency

      import 'package:screenshots/screenshots.dart';

   2. Create the config at start of test

           final config = Config();

   3. Throughout the test make calls to capture screenshots

          await screenshot(driver, config, 'myscreenshot1');

Note: make sure screenshot names are unique across all tests.

Note: to turn off the debug banner, in the integration test's main(), call:

  WidgetsApp.debugAllowBannerOverride = false; // remove debug banner for screenshots

Configuration

Screenshots uses a configuration file to configure a run.
The default config filename is screenshots.yaml:

# A list of screen capture tests
tests:
# Note: flutter driver expects a pair of files eg, main1.dart and main1_test.dart
  - test_driver/main1.dart 
  - test_driver/main2.dart 

# Interim location of screenshots from tests
staging: /tmp/screenshots

# A list of locales supported by the app
locales:
  - en-US
  - de-DE

# A map of devices to emulate
devices:
  ios:
    iPhone XS Max:
    iPhone 11 Pro:
      frame: false # no screen avail so frame must be false
    iPad Pro (12.9-inch) (3rd generation):
      orientation:
        - Portrait # default 
        - LandscapeRight
  android:
    Nexus 6P:
    SM G965F: # a real attached device (frame and orientation disabled)

# Frame screenshots
frame: true

Device Parameters

Individual devices can be configured in screenshots.yaml by specifying per device parameters.

Parameter	Values	Required	Description
frame	true/false	optional	Controls whether screenshots generated on the device should be placed in a frame. Overrides the global frame setting (see example screenshots.yaml above).
orientation	Portrait | LandscapeRight | PortraitUpsideDown | LandscapeLeft	optional	Controls orientation of device during test. Disables framing resulting in a raw screenshot. Ignored for real devices.
build	true(default)/false	optional	Builds and installs app. When set to false, can be used for pre-installed apps that need to be configured before running tests.

frame parameter notes:

• images generated for devices where framing is disabled may not be suitable for upload.
• set to false for devices unknown to screenshots.

orientation parameter notes:

• multiple orientations can be specified. For example:

      iPhone XS Max:
        orientation:
          - Portrait
          - LandscapeRight

• landscape orientation disables framing
  This is because status/navigation bars in landscape mode are currently not implemented.
• orientation on iOS simulators is implemented using an AppleScript script which requires granting permission on first use.

Test Options

In addition to using the default flutter driver mode, tests can also be specified using flutter driver parameters. For example:

tests:
  - --target=test_driver/main1.dart --driver=test_driver/main1_test1.dart
  - --target=test_driver/main2.dart --driver=test_driver/main2_test1.dart

Record/Compare Mode

Screenshots can be used to monitor any unexpected changes to the UI by comparing the new screenshots to previously recorded screenshots. Any differences will be highlighted in a 'diff' image for review.

To use this feature:

1. Add a recording directory to screenshots.yaml

   recording: /tmp/screenshots_record

2. Run a recording to capture expected screenshots:

   screenshots -m recording
   

3. Run subsequent Screenshots with:

   screenshots -m comparison
   

   Screenshots will compare the new screenshots with the recorded screenshots and generate a 'diff' image for each screenshot that does not compare. The diff image highlights the differences in red.

Archive Mode

To generate screenshots for local use, such as generating reports of changes to UI over time, etc... use 'archive' mode.

To enable this mode:

1. Add an archive directory to screenshots.yaml:

   archive: /tmp/screenshots_archive

2. Run Screenshots with:

   $ screenshots -m archive
   

Integration with Fastlane

Since Screenshots is intended to be used with Fastlane, after Screenshots completes, the images can be found in the project at:

android/fastlane/metadata/android
ios/fastlane/screenshots

Images are in a format suitable for upload via deliver and supply.

Tip: One way to use Screenshots with Fastlane is to call Screenshots before calling Fastlane (or optionally call from Fastlane). Fastlane (for either iOS or Android) will then find the images in the appropriate place.

(For a live demo of using Fastlane to upload screenshot images to both store consoles, see demo of Fledge at https://github.com/mmcc007/fledge#demo)

Fastlane FrameIt

iOS images generated by Screenshots can also be further processed using FrameIt's text and background feature.

Adding a device

1. Confirm device is present in screens.yaml.
2. Add device to the list of devices in screenshots.yaml.
3. Confirm a real device is attached, or install an emulator/simulator for device.

If screen is not available, disable framing by setting frame: false for the device.

Config validation

Screenshots will check configuration before running for errors and provide a guide on how to resolve.

Adding a screen

If device does not have a screen in screens.yaml please create an issue to request a new screen.

To submit a new screen please see related README.

Modifying tests based on screenshots environment

In some cases it is useful to know what device, device type, screen size, screen orientation and locale the test is currently running with. To obtain this information use:

final screenshotsEnv = config.screenshotsEnv;

See flutter/flutter#31609 for related flutter driver issue.

Upgrading

To upgrade, simply re-issue the install command

$ pub global activate screenshots

Note: the Screenshots version should be the same for both the command line and in the pubspec.yaml.

1. If upgrading the command line version of Screenshots, also upgrade the version of Screenshots in the pubspec.yaml.
2. If upgrading the version of Screenshots in pubspec.yaml, also upgrade the command line version.

To check the version of Screenshots currently installed:

pub global list

Sample run on Travis and Appveyor

To view Screenshots running with the internationalized example app on macOS and linux in the cloud see:
https://travis-ci.com/mmcc007/screenshots

To view the images generated by Screenshots during a run on travis see:
https://github.com/mmcc007/screenshots/releases/

To view a similar run on windows see:
https://ci.appveyor.com/project/mmcc007/screenshots

• Running Screenshots in the cloud is useful for automating the generation of screenshots in a CI/CD environment.
• Running Screenshots on macOS in the cloud can be used to generate screenshots when developing on Linux and/or Windows.

Related projects

To run integration tests on real devices in cloud:
https://github.com/mmcc007/sylph

To automate releases to both stores:
https://github.com/mmcc007/fledge

Issues and Pull Requests

Issues and pull requests are welcome.