Would it be safe to say that JUnit processes all and only the annotated members in the test-class and sees the rest as plain Java code-- Doesn't look at the un-annotated members.
I haven't gone far deep into JUnit-- yet, but from what i see so far, this is how it is. Looking to pin it down if it's a general case.
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ADD: see the use of its ExpectedException for instance. It's "seeing" its ExpectedException object and setting aside the exception object it's holding when that ExceptionObject is annotated with @Rule. See How do you assert that a certain exception is thrown in JUnit 4 tests?.
If you comment out @Rule, the ExceptionObject declared and instantiated there is a plain class member, just as any other class member-- nothing to do with JUnit this time. JUnit not minding it-- seeing that exception and terminating when that exception occurs.
Looking to see whether this a general rule-- how JUnit operates while working on the code.