how can i test my code wth junit, does i need to make any custimization on codes?

hello there I am using the visual studio code platform to run my code and I want now to est my code using the JUnit extension tester but I have issued and the tester not running what I must do? check this image >>

I am seeing a red line under some words!!
the error message is>> Test cannot be resolved to a typeJava
how can I solve that and make the test run properly?!