### Question:
LeftSideZerosFormatter implements Formatter { @Override public String format(String value) { if (!canBeFormatted(value)) { throw new IllegalArgumentException("Argument value must have only " + formattedLength + " digits at most."); } String formated = value; while (formated.length() < formattedLength) { formated = "0" + formated; } return formated; } LeftSideZerosFormatter(int formattedLength); @Override String format(String value); @Override String unformat(String value); @Override boolean isFormatted(String value); @Override boolean canBeFormatted(String value);  }### Answer:
@Test public void testFormat() { String actual = formatter.format("1234567890"); assertEquals("00001234567890", actual); }