JUnit

Testing ensures that the application is working as expected. As applications increase in size, it can become difficult to test big chunks of code. Testing is done at different levels and in different ways. Testing an application after deployment is called screen testing or system testing. Testing a specific method or a class is called unit testing. It usually involves writing tests for each method of a class. Unit tests can also be written for a group of methods or to test the whole class.

JUnit Architecture

JUnit is a popular unit testing framework. It automates the testing process so that tests can run continually. If there is a change in the code such that the functionality changes, automated testing will catch it. The tests compare the actual output to the expected output to check if the code is working correctly and notify the developer if it is not.

JUnit 5 is the newest release of the framework at the time of writing of this course. It changed the monolithic architecture of JUnit 4 to have separate jar files for the JUnit platform (test engine), Jupiter (JUnit 5 tests), Vintage (JUnit4 tests), and 3rd party extensions while also adding support for new testing patterns. Most IDE’s have built-in support for JUnit 5.