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

##  The `assertLinesMatch()` method
The `assertLinesMatch()` method asserts that two lists of multiple `String` instances match. The matching algorithm used by `assertLinesMatch()` is more complicated than a simple string equality check. This is because output strings are usually templated and may be different in each test execution.
1. The `assertLinesMatch()` method first checks using `String.equals`.
2. If it doesn’t match, the expected string is treated as a regular expression and uses `String.matches` to match again.
3. If it still doesn’t match, it checks if the expected string is a fast-forward marker. For fast-forward markers, the actual strings are fast-forwarded and run the check-in step 1 again.

A fast-forward marker starts and ends with `>>`. If the text between `>>` is an integer, it’s treated as the number of lines to skip. Otherwise, lines are continuously skipped until a match is found.

# The `assertLinesMatch()` method
The `assertLinesMatch()` method asserts that two lists of multiple `String` instances match. The matching algorithm used by `assertLinesMatch()` is more complicated than a simple string equality check. This is because output strings are usually templated and may be different in each test execution.
1. The `assertLinesMatch()` method first checks using `String.equals`.
2. If it doesn’t match, the expected string is treated as a regular expression and uses `String.matches` to match again.
3. If it still doesn’t match, it checks if the expected string is a fast-forward marker. For fast-forward markers, the actual strings are fast-forwarded and run the check-in step 1 again.

A fast-forward marker starts and ends with `>>`. If the text between `>>` is an integer, it’s treated as the number of lines to skip. Otherwise, lines are continuously skipped until a match is found.

Learn how to use the assertLinesMatch() method 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

Assertion: assertLinesMatch()

The `assertLinesMatch()` method