[ZEPPELIN-5879] Migrate Zeppelin Plugins to JUnit5

[Reamer]

What is this PR for?

This pull request migrates the JUnit 4 tests to Junit 5 tests.

What type of PR is it?

Refactoring

What is the Jira issue?

https://issues.apache.org/jira/browse/ZEPPELIN-5879

How should this be tested?

• CI

Questions:

• Does the license files need to update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No

[huage1994]

Hi @Reamer , this PR is a great job. It all looks good to me.
I just have a very small question about this: I noticed that you removed the public modifier from the @Test method but retain the public modifier for methods that are decorated by @BeforEeach .

Is there any special purpose in this? I've tried to remove public modifier for @BeforEeach methods , it looks ok.

[Reamer]

I just have a very small question about this: I noticed that you removed the public modifier from the @Test method but retain the public modifier for methods that are decorated by @BeforEeach .

Is there any special purpose in this?

There is no deeper meaning. My IDE runs the sonarlint plugin, this plugin gives me a little hint to remove the public modifier.
https://rules.sonarsource.com/java/RSPEC-5786

Unfortunately the hint is missing for @beforeeach and other methods, so I overlooked deleting the modifier at this point.

I will go back through the test classes and remove the visibility.

JUnit5 recommends removing the public modifier.
https://junit.org/junit5/docs/current/user-guide/#writing-tests-classes-and-methods