Gain insights into JUnit 5, explore its advantages over JUnit 4, and delve into its features like assertions, parameterized tests, dependency injection, and test execution order. Discover hands-on projects to cement your skills.

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JUnit 5 is a standard framework for unit testing in Java. Released in 2017, JUnit 5 is a major improvement over JUnit 4 and supports a lot of new methods. Many projects have migrated from JUnit 4 to JUnit 5. JUnit 5 is also the default test framework for new projects. JUnit 5 is composed of three sub-projects: JUnit Platform, JUnit Jupiter, and JUnit Vintage. Details of these sub-projects are discussed in the course.

This course first discusses the advantages of JUnit 5 over the previous versions and then jumps directly into tests. The course includes discussion on assertions, assumptions, tagging and filtering, nested tests, dependency injection, repeated tests, parameterized tests, dynamic tests, test instance lifecycle, extension model, JUnit 4 migration, JUnit platform, and test execution order. 

By the end of this course, you’ll be deeply familiar with unit testing in JUnit 5. There’s also a little project for you at the end to put your newly acquired skills to the test.

All About JUnit5

## Overview
We’ve discussed built-in sources of parameters for parameterized tests. We can also create new sources of arguments using the `@ArgumentsSource` annotation and the `org.junit.jupiter.params.provider.ArgumentsProvider` interface. The `@ArgumentsSource` annotation specifies the implementation of `ArgumentsProvider` to use for providing the arguments. The `ArgumentsProvider` only has one method, `Stream<? extends Arguments> provideArguments(ExtensionContext context) throws Exception`, to return a stream of `Arguments` objects.
## The `@JsonFileSource` annotation
To demonstrate custom sources of arguments, we’ll create a source of arguments that resolves JSON file arguments. The JSON file should contain an array of objects. Each object in the array is mapped to an `Arguments` object.  Because the properties in a JSON object aren’t ordered, we need to specify the mapped property name for each parameter.


The `@JsonFileSource` annotation uses `@ArgumentsSource` to specify the `JsonArgumentsProvider` implementation class.

# Overview
We’ve discussed built-in sources of parameters for parameterized tests. We can also create new sources of arguments using the `@ArgumentsSource` annotation and the `org.junit.jupiter.params.provider.ArgumentsProvider` interface. The `@ArgumentsSource` annotation specifies the implementation of `ArgumentsProvider` to use for providing the arguments. The `ArgumentsProvider` only has one method, `Stream<? extends Arguments> provideArguments(ExtensionContext context) throws Exception`, to return a stream of `Arguments` objects.
# The `@JsonFileSource` annotation
To demonstrate custom sources of arguments, we’ll create a source of arguments that resolves JSON file arguments. The JSON file should contain an array of objects. Each object in the array is mapped to an `Arguments` object.  Because the properties in a JSON object aren’t ordered, we need to specify the mapped property name for each parameter.


The `@JsonFileSource` annotation uses `@ArgumentsSource` to specify the `JsonArgumentsProvider` implementation class.

Learn how to create sources of arguments in JUnit 5.

Getting Started

Writing Basic Tests

Annotations, Tagging, and Filtering

Nested tests in JUnit 5

Dependency Injections

Parameterized and Dynamic Tests

Test Instance Lifecycle in JUnit 5

Extension Model

JUnit Platform

Test Execution Order

Conclusion

Library Management System

Sources of Arguments in Parameterized Tests

Overview