### Question:
TickUnits implements TickUnitSource, Cloneable, Serializable { @Override public boolean equals(Object obj) { if (obj == this) { return true; } if (!(obj instanceof TickUnits)) { return false; } TickUnits that = (TickUnits) obj; return that.tickUnits.equals(this.tickUnits); } TickUnits(); void add(TickUnit unit); int size(); TickUnit get(int pos); @Override TickUnit getLargerTickUnit(TickUnit unit); @Override TickUnit getCeilingTickUnit(TickUnit unit); @Override TickUnit getCeilingTickUnit(double size); @Override Object clone(); @Override boolean equals(Object obj);  }### Answer:
@Test public void testEquals() { TickUnits t1 = (TickUnits) NumberAxis.createIntegerTickUnits(); TickUnits t2 = (TickUnits) NumberAxis.createIntegerTickUnits(); assertEquals(t1, t2); assertEquals(t2, t1); }