### Question:
Range implements Serializable { public int length() { return getEnd() - getStart(); } private  Range(final int start, final int end); static Range withOnly(final int integer); static Range between(final int start, final int end); static Range withLength(final int start, final int length); int getStart(); int getEnd(); int length(); boolean isEmpty(); boolean intersects(final Range other); boolean contains(final int integer); boolean isSubsetOf(final Range other); Range[] partitionWith(final Range other); Range offsetBy(final int offset); @Override String toString(); @Override int hashCode(); @Override boolean equals(final Object obj); boolean startsBefore(final Range other); boolean endsBefore(final Range other); boolean endsAfter(final Range other); boolean startsAfter(final Range other); Range[] splitAt(final int integer); Range[] splitAtFromStart(final int length); Range combineWith(Range other); Range expand(int startDelta, int endDelta); Range restrictTo(Range bounds);  }### Answer:
@Test public void lengthTest() { assertEquals("withLength length", 5, Range.withLength(10, 5).length()); assertEquals("between length", 5, Range.between(10, 15).length()); assertEquals("withOnly 10 length", 1, Range.withOnly(10).length()); }