### Question:
DateTime implements Comparable<DateTime> { public static DateTime valueOf(StringOption timeString, DateTime.Format format) { if (timeString == null) { throw new IllegalArgumentException("timeString must not be null"); } if (format == null) { throw new IllegalArgumentException("format must not be null"); } if (timeString.isNull()) { return null; } return valueOf(timeString.getAsString(), format); } DateTime();  DateTime(long elapsedSeconds);  DateTime(int year, int month, int day, int hour, int minute, int second); long getElapsedSeconds(); void setElapsedSeconds(long elapsed); int getYear(); int getMonth(); int getDay(); int getHour(); int getMinute(); int getSecond(); @Override int hashCode(); @Override boolean equals(Object obj); @Override int compareTo(DateTime o); @Override String toString(); static DateTime valueOf(StringOption timeString, DateTime.Format format); static DateTime valueOf(String timeString, DateTime.Format format); static final String FORMAT; }### Answer:
@Test public void parse_null() { StringOption option = new StringOption(null); DateTime time = DateTime.valueOf(option, DateTime.Format.SIMPLE); assertThat(time, is(nullValue())); }