### Question:
BigIntegerWrapper extends AbstractWrapper<BigInteger> implements NumberWrapper<BigInteger> { @Override public void increment() { BigInteger value = doGet(); if (value != null) { doSet(value.add(BigInteger.ONE)); } } BigIntegerWrapper();  BigIntegerWrapper(BigInteger value); @Override void set(Number v); @Override void increment(); @Override void decrement(); @Override R accept(WrapperVisitor<R, P, Q, TH> visitor, P p, Q q);  }### Answer:
@Test public void testIncrement() { BigIntegerWrapper wrapper = new BigIntegerWrapper(new BigInteger("10")); wrapper.increment(); assertEquals(new BigInteger("11"), wrapper.get()); }