### Question:
PhoneNumberCleaner implements Cleaner { public String clean(String value) { String orig = value; boolean initialplus = findPlus(value); value = sub.clean(value); if (value == null) return null; boolean zerozero = !initialplus && value.startsWith("00"); if (zerozero) value = value.substring(2); CountryCode ccode = findCountryCode(value); if (ccode == null) { if (initialplus || zerozero) return orig; return value; } else { value = value.substring(ccode.getPrefix().length()); if (ccode.getStripZero() && value.startsWith("0")) value = value.substring(1); if (ccode.isRightFormat(value)) return "+" + ccode.getPrefix() + " " + value; else return orig; } } PhoneNumberCleaner(); String clean(String value);  }### Answer:
@Test public void testEmpty() { assertTrue(cleaner.clean("") == null); }