### Question:
IPNetwork extends PGcidr implements Serializable, Cloneable, Comparable<IPNetwork> { public byte[] getNetmaskAddress() { return netmaskAddress; } IPNetwork();  IPNetwork(PGcidr net);  IPNetwork(String net); @Override void setValue(String v); final void init(); byte[] getBroadcastAddress(); void setBroadcastAddress(byte[] broadcastAddress); byte[] getWildcard(); void setWildcard(byte[] wildcard); byte[] getNetmaskAddress(); void setNetmaskAddress(byte[] netmaskAddress); boolean isV6(); void setV6(boolean v6); void setEmbeddedIPv4(boolean embeddedIPv4); @Override boolean equals(Object obj); @Override int hashCode(); @Override int compareTo(IPNetwork o); boolean hasEmbeddedIPv4(); IPTarget getHighestTarget(); IPTarget getLowestTarget(); boolean contains(IPTarget ip); byte[] getAddr(); IPNetwork next(); @Override String toString();  }### Answer:
@Test public void testInitializerPGcidr() throws Exception { IPNetwork net = new IPNetwork(); Assert.assertEquals("Empty IPNetwork must not have a network address", null, net.getNetmaskAddress()); }