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

# Using repeated tests
We may occasionally want to run a test method multiple times. JUnit 5 has the `org.junit.jupiter.api.RepeatedTest` annotation to easily support this requirement. We simply need to use `@RepeatedTest` instead of `@Test` to annotate methods and specify the total number of repetitions. Each repetition of the repeated test behaves like a regular test method with `@Test`.

import org.junit.jupiter.api.RepeatedTest;
import org.junit.jupiter.api.RepetitionInfo;

@DisplayName("TestReporter")
public class ReporterTest {
      @RepeatedTest(3) 
      @DisplayName("simple") 
      void simpleTest() {
      }

      @RepeatedTest(3)
      @DisplayName("a little complex")
      void testWithRepititionInfo(RepetitionInfo repetitionInfo) {
         assertNotEquals(2, repetitionInfo.getCurrentRepetition());
      }

}

In the code above:
- **Lines 6–9:** The `simpleTest()` function repeats three times because we passed `3` in the `@RepeatedTest` annotation. Each test has its own display name, for example, `repetition 1 of 3`.
- **Lines 11–15:** We use `RepititionInfo` and extract information regarding the repetition number using the `getCurrentRepitition()` method. As we can see from the output, the test names `repetition 1 of 3` and `repetition 3 of 3` pass because two is not equal to one or three. However, the test name `repetition 2 of 3` fails.
Although not given in this code, there is another method in `RepetitionInfo` called `getTotalRepetitions()`, which as the name suggests outputs the total number of repetitions of the corresponding `@RepeatedTest` method.


Although it’s not given in this code, there’s another method in `RepetitionInfo` called `getTotalRepetitions()`. This method outputs the total number of repetitions of the corresponding `@RepeatedTest` method.

The display name can be customized using the name attribute of `@RepeatedTest`. We can also use placeholders in the name attribute to generate dynamic text for each repetition.



Learn how to use the @RepeatedTest annotation 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

Repeated Tests

Using repeated tests