Gain insights into configuring and utilizing JUnit 5 for Java unit testing. Learn about writing effective unit tests, integrating assertions, assumptions, parameterized tests, and their significance.

Junit 5 is the most popular and widely used Java unit testing framework. In this course, you will learn step by step, how to configure and use JUnit 5 testing framework. This course will teach you how to write unit tests with JUnit 5, covering topics like why unit tests are important, the structure of good unit tests, assertions, assumptions and parameterized tests and more.

Java Unit Testing with JUnit 5

# assertNull() method ###

Assertions API provide static `assertNull()` method. This method helps us in validating that the particular object is null. This method takes an actual value and checks whether it is `null` or not.

- If the actual value is **null** then test case will pass.
- If the actual value is **not null** then test case will fail.


There are basically three overloaded methods for assertNull which are described below:-

public static void assertNull(Object actual)

public static void assertNull(Object actual, String message)

public static void assertNull(Object actual, Supplier<String> messageSupplier)
  

1. `assertNull(Object actual)` - It asserts whether actual value is null or not.

2. `assertNull(Object actual, String message)` - It asserts whether actual value is null or not. In case, if the actual value is not null then the test case will fail with a provided message.  

3. `assertNull(Object actual, Supplier<String> messageSupplier)` - It assert whether actual value is null or not. In case, if the actual value is not null then the test case will fail with a provided message through Supplier function. The main advantage of using Supplier function is that it lazily evaluates to String only when the test case fails.

This lesson demonstrates how to use assertNull() method in JUnit 5 to assert test conditions. 

Getting Started

Assertions in Junit 5

Junit 5 Test Lifecycle Callbacks

Display Names

Dependency Injection for Constructors and Methods

Assumptions in Junit 5

Disable or Enable Tests in Junit 5

Nested Tests in Junit 5

JUnit 5 Integration with Maven

Parameterized Tests in Junit 5

Repeated Tests in Junit 5

Appendix

assertNull() method

assertNull() method