### Question:
Context implements Externalizable, Loggeable, Pausable, Cloneable { public void persist (Object key) { Object value = get(key); if (value instanceof Serializable) getPMap().put (key, value); } Context(); void put(Object key, Object value); void put(Object key, Object value, boolean persist); void persist(Object key); void evict(Object key); T get(Object key); T get(Object key, T defValue); synchronized T remove(Object key); String getString(Object key); String getString(Object key, String defValue); void dump(PrintStream p, String indent); @SuppressWarnings("unchecked") synchronized T get(Object key, long timeout); void writeExternal(ObjectOutput out); void readExternal(ObjectInput in); @Override Context clone(); @Override boolean equals(Object o); @Override int hashCode(); synchronized Map<Object,Object> getMap(); synchronized LogEvent getLogEvent(); synchronized Profiler getProfiler(); synchronized Result getResult(); void log(Object msg); void checkPoint(String detail); void setPausedTransaction(PausedTransaction p); PausedTransaction getPausedTransaction(); PausedTransaction getPausedTransaction(long timeout); void setTimeout(long timeout); long getTimeout(); synchronized void resume(); boolean isTrace(); void setTrace(boolean trace);  }### Answer:
@Test public void testPersist() throws IOException, ClassNotFoundException { Context context = new Context(); context.put ("A", "ABC"); context.put ("B", "BCD"); context.persist("A"); context.persist("B"); Context deser = Serializer.serializeDeserialize(context); assertEquals(deser.get("A"), "ABC"); assertEquals(deser.get("B"), "BCD"); deser.evict("A"); deser = Serializer.serializeDeserialize(deser); assertEquals(deser.get("B"), "BCD"); assertNull(deser.get("A"), "A should be null"); }