Testing tool for Android

Testing is a risky software development task because of this 
app quality improves, make sure better user satisfaction, and reduce overall development time spent on fixing defects.

Here are the tools that help you test your mobile apps for the Android platform. There are some library support for android testing -

By these APIs build are quick and run test code for you application. It includes JUnit 4 and functional user interface tests.Support Library includes the following test automation tools-
 
AndroidJUnitRunner: The AndroidJUnitRunner class is a JUnit test runner allows you to run JUnit 3 or JUnit 4-style test classes on Android devices, along with those that have Espresso and UI Automator testing frameworks. The test runner manages loading test package and the app under test to a device, running your tests, and reporting test results. This class replaces the InstrumentationTestRunner class, which only supports JUnit 3 tests.

Test runner include some key fetures:

JUnit support

Access to instrumentation information

Test sharding
Test filtering

Espresso: The Espresso testing framework offers a set of APIs to create UI tests to test user flows within an app. These APIs allow you to write automated UI tests that run reliably. Espresso is appropriate for writing white box -style automated tests, while the test code  makes use of implementation code details from the app under test

Espresso testing framework include some key features:

Flexible APIs for adapter and view matching in target apps. 

An extensive set of action APIs to automate UI interactions.

UI thread synchronization to improve test reliability. 

UI Automator: The UI Automator testing framework provides a set of APIs to build UI tests that perform interactions on system apps and user apps . The UI Automator APIs allows us to perform operations such as app launcher in a test device or opening the Settings menu. The UI Automator testing framework is well-suited for writing black box-style automated tests, where the test code does not rely on internal implementation details of the target app.

UI Automator testing framework has some key features :

A viewer to inspect layout hierarchy.

An API to retrieve state information and perform operations on the target device. 

APIs that support cross-app UI testing. 

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