Which unit testing library do test engineers usually use to test Java programs?

Test engineers often use a variety of different unit testing libraries when testing Java programs, and the specific choice depends on the needs of the project and the preferences of the team. Let’s first look at some commonly used Java unit testing libraries and some of their characteristics:

1.JUnit:

·Description: JUnit is one of the most widely used unit testing libraries in Java. It supports two major versions of JUnit 4 and JUnit 5. JUnit 5 introduces some new features, such as extended models, parameterized testing, conditional testing, etc.

·Features:

·Annotations are provided to mark test methods, such as @Test for identifying test methods.

·Supports Test Suites, allowing you to organize and run a set of test classes.

· Provides assertion methods, such as assertEquals, assertTrue, assertThrows, etc., for verifying expected results.

·Extensions can be used to customize test behavior, such as test life cycle, dependency injection, etc.

2.TestNG:

·Description: TestNG is another popular Java unit testing library that provides richer functionality for testing and organizing test cases.

·Features:

·Support Test Groups, which can run tests according to different organizational structures.

·Provides parameterized testing, allowing the same test method to be run on multiple sets of input data.

·Support parallel test execution to improve test speed.

·Support dependency test methods to ensure that tests are executed in the specified order.

·Provides rich report and log functions to facilitate test result analysis.

3.Spock:

·Description: Spock is a testing framework based on the Groovy language, but can be seamlessly integrated with Java code. It is characterized by legibility and expressiveness.

·Features:

·Write test cases using clear DSL (Domain Specific Language) syntax, increasing readability.

·Supports data-driven testing by defining different input data sets through where blocks.

·You can use setup and cleanup blocks to set up preparation and cleanup operations before and after testing.

·Supports mocking and stubbing objects to easily simulate external dependencies.

·Rich reporting and logging functions.

4.Mockito:

·Description: Mockito is a library for creating mock objects (Mocks), usually used with JUnit or TestNG, for simulating external dependencies and behavior verification.

·Features:

·Mainly used to simulate external dependencies, such as database access, network requests, etc.

· Provides an easy-to-use API to define the behavior of mock objects.

· Method calls to mock objects can be verified to ensure they are called as expected.

·Support parameter matcher for more flexible verification of method parameters.

·Can be used in conjunction with other unit testing libraries, such as JUnit or TestNG.

5.JUnit Jupiter + Mockito:

·Description: This is a common way to use JUnit 5 with Mockito. JUnit Jupiter is used for writing test cases, while Mockito is used for mocking external dependencies.

·Features:

·JUnit Jupiter provides test framework support, including life cycle management, assertions, etc.

·Mockito is used to simulate and verify external dependencies.

·This combination combines two powerful tools for writing clean, maintainable unit tests.

Which unit testing library to choose depends on the needs of the project, the experience of the team, and personal preference. Generally, JUnit is a good starting point, while when more advanced functionality is required, consider other libraries such as TestNG or Spock. Mockito is often used in conjunction with these libraries to simulate external dependencies.