Introduce JUnit 5 and AssertJ dependencies

[PatrickRen]

Search before asking

• I searched in the issues and found nothing similar.

Motivation

In order to align with the test framework used in Apache Flink and improve the experience of writing test code, we introduce:

• JUnit 5 as the framework for all new tests
• AssertJ for all assertions in new tests

Note that introducing JUnit 5 won't break existing JUnit 4 style tests, and JUnit 5 provides compatibility running environment (junit-vintage-engine) for JUnit 4 tests.

Solution

No response

Alternatives

No response

Anything else?

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!