Sample Testing is insufficient. An incorrect submission such as this currently passes the kata.

The following is the smallest case that will fail such a solution:

    assertEquals(6, Beer.countBottles(11));

When Random Tests are implemented, they shoud also be sure to include a minimum number of such cases.

No Random Tests

Sample tests appear invalid:

Failed to detect class name:
Beer.assertEquals(7, Beer.countBottles(12));
Beer.assertEquals(26, Beer.countBottles(40));
Beer.assertEquals(6, Beer.countBottles(10));

Please see https://docs.codewars.com/languages/java/junit for the basic testing harness setup.

You may also wish to clarify the relationship between Euros and cents for non-European warriors.