Pragmatic Unit Testing in Java with JUnit, 3rd Edition

ZOM: Zero and One Done, Now Testing Many

You’ve written a zero-based test (a test for the “zero” case) and a one-based test so far. It’s time to slam out a many-based test:

utj3-credit-history/09/src/test/java/credit/ACreditHistory.java

@Test
void withMultipleRatingsDividesTotalByCount() {
   creditHistory.add(new CreditRating(780));
   creditHistory.add(new CreditRating(800));
   creditHistory.add(new CreditRating(820));

   var result = creditHistory.arithmeticMean();

   assertEquals(800, result);
}

You can create this test by copying the one-based test, duplicating a couple of lines in order to add a total of three credit ratings, and changing the expected value for the assertion. It should pass. Break it; it should fail. Fix ...