Espresso - A testing framework for Android to make it easy to write reliable user interface tests.

Retrofit2 - A type-safe HTTP client for Android and Java.

RxJava2 - A library for composing asynchronous and event-based programs by using observable sequences.

RxPermissions - This library allows the usage of RxJava with the new Android M permission model.

RxBinding - RxJava binding APIs for Android UI widgets from the platform and support libraries.

Glide - An image loading and caching library for Android focused on smooth scrolling.

Android Architecture Component - A new collection of libraries that help you design robust, testable, and maintainable apps.

LeakCanary - A memory leak detection library for Android and Java.

Butter Knife - Bind Android views and callbacks to fields and methods.

Dagger2 - A fast dependency injector for Android and Java.

Timber - A logger with a small, extensible API which provides utility on top of Android's normal Log class.