@Nested is used to signal that the annotated class is a nested,
non-static test class (i.e., an inner class) that can share
setup and state with an instance of its enclosing class. The enclosing class may be a top-level test class or
another @Nested test class, and nesting can be arbitrarily deep.
Test Instance Lifecycle
A @Nested test class can be configured with its own
TestInstance.Lifecycle mode which may differ from that of an enclosing test
class.
A @Nested test class cannot change the TestInstance.Lifecycle
mode of an enclosing test class.