Introduction to JUnit 5

The famous Java unit testing framework JUnit 4 has been out for a long time. At that time, I found that JUnit 5 was in the beta version, so I was ready to write an article to introduce JUnit 5 However, because it is still a beta version, some places are not perfect, and I'm a little lazy and didn't write well. I suddenly think of it these days. I checked it on the official website and found that on September 10, the official version of JUnit 5 finally came out! Then I'll just rewrite the article and introduce you to the latest JUnit framework.

Frame structure

Compared with JUnit 4, JUnit 5 has a very clear structure and provides good support for extended functions such as custom plug-ins and IDE test execution. This can be seen from the project structure.

JUnit Platform

The package name of this group is org junit. Platform, as can be seen from the name, the main function of this group is to serve as the basic platform of the test framework. The modules under this package include basic API, execution engine and executor, basic command line execution function, command line interface, Maven and gradle test plug-ins and other basic functions.

JUnit Jupiter

Jupiter is the code of JUnit 5. The modules under this package contain the main functions of JUnit 5. If we want to use JUnit 5, we must include this set of modules.

JUnit Vintage

Vintage is the code of the old version of JUnit. The module under this package allows us to run the tests of old JUnit 3 and 4 on the new JUnit platform.

Import class library

When JUnit 5 was still in the testing stage, there were examples of integrating JUnit 5 in Maven and gradle in the official documents. But in the official version, the content of this part disappeared, leaving only links to two sample projects for our own reference (copy and paste).

Using maven

Junit5 Maven consumer is the official Maven example. I was going to post the relevant POM configuration here, but Maven's configuration is too long, so I'll forget it. If necessary, please check the POM configuration of this project yourself.

Now the constructor and test method of the test class can accept parameters. The parameterresolver interface defines how to inject parameters at run time. Several built-in can let us get the information of test case runtime.

The first is testinfoparameterresolver. If there is an instance of testInfo type on the method, the JUnit 5 framework will automatically inject the instance. Several methods of this instance can let us obtain the name, display name, label and other information of the test class and test method.

Note that only static inner classes can use nested annotations. In addition, because Java does not allow static methods in internal classes, it cannot have @ beforeall and @ afterall annotations. If you want to break this limit, you need to add @ testinstance (lifecycle. Per_class) annotation on the nested inner class. For details, see test instance lifecycle.

After the modification, run the test again. Sure enough, there is no problem. Of course, in order to learn and use, I also refer to the package of JUnit 4, so this conflict occurs. If there are no special requirements, it is recommended to import only the jar package of JUnit 5 to prevent confusion. Of course, you can import everything, but you need to be careful not to write JUnit 4 annotations on JUnit 5 tests. Finally, I attach a small example of my test, which can be seen by interested students.