Guru99 is a website worth to mention. Their comprehensive tutorials contain beautifully annotated screenshots. Their goal is to provide fun and free education for everyone.
Sometimes I prefer video tutorials but they can be time consuming so a source like this is more accesible with its content.
The JUnit course covers;
- JUnit Basics like Introduction, Test framework, Download and Install Guide
- Introduces Junit Annotation, API, Assert and JUnit Test Suite
- Advanced topics like Ignore Test, Exception Test, ErrorCollector and Parameterized Test