JoiningExpressionImpl implements JoiningExpression<T> { @Override public CharSequence separator() { return separator; } JoiningExpressionImpl(
            final CharSequence separator,
            final CharSequence prefix,
            final CharSequence suffix,
            final List<ToString<T>> expressions); @Override List<ToString<T>> expressions(); @Override CharSequence prefix(); @Override CharSequence suffix(); @Override CharSequence separator(); @Override String apply(T object);  }
@Test void separator() { assertEquals(SEPARATOR, instance.separator()); }