Mockito vs Robolectric: What are the differences?

Introduction

In the world of software development, two popular testing frameworks for Java applications are Mockito and Robolectric. Although both frameworks are used for testing, they have some key differences that make them suitable for different purposes. In this article, we will explore these differences and highlight their specific features and use cases.

1. Mockito: Known as a mocking framework, Mockito is primarily used for testing behavior-driven development (BDD) and for creating fake objects or mocks of interfaces and classes. It allows developers to create stubs and mocks that simulate the behavior of real objects, making it easier to isolate and test specific code components. With Mockito, you can verify interactions between objects and test their behavior without relying on a real implementation. This framework focuses on the testing of individual units of code, specifically methods and classes.

2. Robolectric: Unlike Mockito, Robolectric is a framework that enables developers to perform unit tests on Android applications without the need for an emulator or a connected device. It provides a simulated and controlled environment for testing, allowing developers to run tests on different versions of Android within the IDE. Robolectric offers a vast array of shadow objects that can be used to simulate Android components, such as activities, services, and intents. This framework is specifically designed for testing the interaction between components within an Android application, including UI testing.

3. Use Case Differences: Mockito is primarily used for unit testing standalone code components, such as methods and classes, without the need for a real implementation or dependencies. It focuses on isolating and testing individual units of code, ensuring they behave as expected. On the other hand, Robolectric is specifically designed for testing Android applications and their components. It allows developers to test interactions between different components, including UI testing and verifying how these components behave in various scenarios.

4. Test Execution Environment: Mockito does not require any specific execution environment and can be run directly within a Java testing framework, such as JUnit or TestNG. It can be used in both standard Java applications and Android applications. In contrast, Robolectric requires a custom test runner and a specific execution environment to simulate Android components. It needs to be run within an IDE that supports Robolectric or a continuous integration server with the necessary setup for Android testing.

5. Integration with Android SDK: Mockito does not have any direct integration with the Android SDK as it is primarily designed for unit testing Java code. It can be used in Android projects by mocking Android dependencies, but it does not provide the ability to simulate Android components. On the other hand, Robolectric seamlessly integrates with the Android SDK and provides a comprehensive set of shadow objects that accurately simulate Android components. This allows developers to test Android-specific functionality, such as UI interactions and resource loading.

6. Speed of Execution: Mockito is known for its simplicity and speed of test execution. Since it focuses on unit testing standalone code components, it does not require any emulator or device setup, resulting in faster test execution times. Robolectric, on the other hand, involves the setup and simulation of Android components, which can slow down the test execution process. Although measures have been taken to improve the execution speed in Robolectric, it may still be slower compared to Mockito due to the complexity of the simulated Android environment.

In summary, Mockito is a mocking framework primarily used for unit testing individual code components in Java applications, while Robolectric is a framework specifically designed for testing Android applications and their components, including UI testing. Mockito focuses on creating mocks and stubs to simulate behavior, while Robolectric allows for the simulation of Android components without the need for an emulator or connected device. Mockito does not directly integrate with the Android SDK, whereas Robolectric provides seamless integration and simulation of Android components. Despite its simplicity, Mockito offers faster test execution times compared to Robolectric due to the latter's involvement of simulating the Android environment.