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Automated E2E testing involving intercommunication between two or more mobile applications running in different devices or emulators.
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Kraken is an open source automated android and web E2E testing tool that supports and validates scenarios that involve the inter-communication between two or more users. It works in a Black Box manner meaning that it is not required to have access to the source code of the application but instead it can be run with the APK (Android package file format) and web page URL. Kraken uses signaling for coordinating the communication between the devices using a file based protocol.

Kraken is partially supported by a Google Latin America Research Award (LARA) 2018





Kraken uses calabash-android and selenium-webdriver for running automated E2E tests in each device or emulator and cucumber for running your feature files written with Gherkin sintax.

🔨 Installation


Kraken requires Ruby 2.20 or higher but we recommend using ~2.3 version. We use calabash-android for mobile testing, you can check their prerequisites at this link. For web testing we use selenium-webdriver, you can check their prerequisites as well at this link.

  • Ruby at least version 2.3.1
  • Java JDK
  • Android SDK
  • Chromedriver (Version ~83 recommended) or Geckodriver (Only if you use Kraken web)

You need to have configured ANDROID_HOME, ANDROID_HOME/platform_tools and JAVA_HOME in your environment variables.

Installing and managing Kraken Gem is done through the gem command. To install Kraken’s gem run the following command.

$ gem install kraken-mobile

NOTE: If you are having trouble running Kraken in your Windows operating system refer to the this guide specifying steps to solve this issues.


Signaling is a protocol used for the communication of two or more devices running in parallel. It is based in the idea that each browser, emulator or real device has a communication channel where he can receive signals sent from other devices which contain information or actions that are supposed to be executed. This type of protocol is commonly used in automated mobile E2E testing tools that validate scenarios involving the inter-communication and collaboration of two or more applications.

Writing your first test

Generate cucumber feature skeleton

First you need to generate the cucumber feature skeleton where your tests are going to be saved. To achieve this you should run kraken-mobile gen. It will create the skeleton in your current folder like this:

| |_app_installation_hooks.rb
| |_app_life_cycle_hooks.rb
| |_env.rb
| |_mobile_steps.rb
| |_step_definitions
| | |_web_steps.rb
| |_support
| | |_app_life_cycle_hooks.rb

Write a test

The features goes in the features foler and should have the “.feature” extension. You can start out by looking at features/my_first.feature. You should also check calabash predefined steps.


In Kraken each feature is a test and each scenario within a feature is a test case that is run in a device. Each device is identified as an user and numbered from 1 to N. Ex: @user1, @user2, @user3. To check what is the number of a given device you should run kraken-mobile devices.

List of devices attached
user1 - emulator-5554 - Android_SDK_built_for_x86
user2 - emulator-5556 - Android_SDK_built_for_x86

After identifying what number each device has, you can write your test case giving each scenario the tag of a given device like so:

Feature: Example feature

  Scenario: As a first user I say hi to a second  user
  Given I wait
  Then I send a signal to user 2 containing "hi"

  Scenario: As a second user I wait for user 1  to say hi
  Given I wait for a signal containing "hi"
  Then I wait

Kraken steps

Kraken offers two main steps to help synchronizing your devices.

Signaling steps

To wait for a signal coming from another device for 10 seconds that is Kraken default timeout use the following step.

Then /^I wait for a signal containing "([^\"]*)"$/

To wait for a signal coming from another device for an specified number of seconds use the following step

Then /^I wait for a signal containing "(  [^\"]*)" for (\d+) seconds$/

To send a signal to another specified device use the following step

Then /^I send a signal to user (\d+) containing "([^\"]*)"$/

Signaling functions

Each device has an internal Kraken implementation of the signaling steps using the following functions.

read_signal(content, time_out)

Waits for a signal with the specified content. This functions waits for the specified number of seconds in the timeout parameter before throwing an exception if specified.


Writes signal content to a device inbox.

📱Kraken Mobile

Running your tests

To run your test:

$ kraken-mobile run <apk>

Kraken with the help of Calabash-Android will install an instrumentation along with your app and will start your tests in all devices connected (Check Kraken Settings section in order to learn how to specify in what devices your tests should be run).

🦍 Mobile Monkey execution

Kraken offers the possibility of generating random GUI events by using Android ADB monkey as well as its own implementation based in the idea of sending and reading random signals.

Android’s ADB Monkey

To execute ADB monkey Kraken offers the following command specifying the number of events to be executed:

Then I start a monkey with (\d+) events

Kraken’s own monkey

Kraken extended the ADB monkey behavior by executing GUI events only in buttons and clickable views or inputs by offering the following command:

Then I start kraken monkey with (\d+) events

XML snapshot

Kraken makes it possible to save the XML presented by the current view in a specific device, this is convenient to identify view ids, asserting the correct XML is presented after an action has being completed or running static analyzing tools.

Saving the snapshot

To save the snapshot of the current view, Kraken offers the following step specifying where the file is going to be saved:

Then I save device snapshot in file with path "([^\"]*)"

🌎 Kraken Web

Kraken is extended to run also in web browsers and orchestrate the communication with other browsers running different websites or mobile applications that are being executed on physical devices or emulators. With the help of ChromeDriver/Geckodriver, selenium-webdriver and Cucumber we run test scenarios using Gherkin syntax as well as Kraken predefined signaling steps described before.

Specifying a web user in a test

To specify that user is going to be run in a web browser instead of a mobile device you need to tag the scenario with @web. If a scenario is not tagged with @web Kraken will assume that is a mobile user and will attempt to run all steps in a mobile manner.

Feature: Example feature

  @user1 @web
  Scenario: As a first user I say hi to a second  user
	Given I navigate to page "https://www.gmail.com/"
    Then I send a signal to user 2 containing "hi"

  @user2 @web
  Scenario: As a second user I wait for user 1  to say hi
    Given I wait for a signal containing "hi"
	Then I navigate to page "https://www.gmail.com/"

This scenario will open two web browsers and execute the signaling between them.

Web steps

To see a list of all web steps available in Kraken, visit the following link.

Executing web only scenarios

To run a test that only contains web users and as a result does not require an APK file, run the following command:

$ kraken-mobile run

Kraken with the help of selenium-webdriver will start all required browsers and run your test scenario.

Specifying in what browser Kraken will run

Kraken uses ChromeDriver and Chrome as default web browser but provides support for Firefox and Geckodriver. To specify that your test is going to be run in Firefox, specify the environment variable BROWSER when running your tests as follows:

$ BROWSER=firefox kraken-mobile run

Note: Make sure that you have Geckodriver and Firefox installed previously.

🦍 Web Monkey execution

Kraken has implemented it's own monkey behavior by executing random GUI events in buttons, clickable views and inputs by offering the following command:

Then I start kraken monkey with (\d+) events

Kraken Settings

Kraken uses kraken_mobile_settings.json to specify in what devices the tests should be run.

Generate settings file

The following command will show you the available connected devices or emulators and let you choose which ones you want to use.

$ kraken-mobile setup

Run tests with settings file

$ kraken-mobile run <apk> --configuration=<kraken_mobile_settings_path>

🗯 Extended Kraken functionalities

In the following sections we provide specification for shared functionality between Kraken mobile and web as well as some examples of Kraken in action.

Properties file

Kraken uses properties files to store sensitive data such as passwords or api keys that should be used in your test cases.

Generate properties file

The properties files should be a manually created JSON file with the following structure.

    "@user1": {
        "PASSWORD": "test"
    "@user2": {
        "PASSWORD": "test2"

Use properties file in your test

You can use the specified properties using the following sintax.

Scenario: As a user
    Given I wait
    Then I see the text "<PASSWORD>"

Run tests with settings file

kraken-mobile run <apk> --properties=<kraken_mobile_properties_path>

Use fake strings in tests

Kraken offers a Fake string generator thanks to the Ruby gem Faker, the list of supported faker types are listed as follows:

  • Name
  • Number
  • Email
  • String
  • String Date

Use a faker in a test

Kraken keeps a record of every Fake string generated, thats why each string will have an id associated. To generate a Faker string you need to follow the structure “$FAKERNAME_ID”.

Scenario: As a user
    Given I wait
    Then I enter text "$name_1" into field with id "view"

Reusing a fake string

As mentioned before, Kraken keeps record of every string generated with an id given to each string, this gives you the possibility of reusing this string later in your scenario. To reuse a string you can you need to append a $ character to the fake string as follows:

Scenario: As a user
    Given I wait
    Then I enter text "$name_1" into field with id "view"
    Then I press "add_button"
    Then I should see "$$name_1"


Application Video Feature File Steps Definition Properties file Settings File Report Link
Infinite Words video .feature --- --- --- report
QuizUp video .feature stepsDef --- --- report
Spotify/Shazam video .feature stepsDef .json .json report
Spunky video .feature stepsDef --- --- report
Picap video .feature stepsDef .json --- report
AskFM video .feature stepsDef --- --- report
Stick Men Fight video .feature --- --- --- report
Tic Tac Toe video .feature stepsDef --- --- report
Tumblr video .feature stepsDef .json --- report
F3 video .feature stepsDef .json --- report