### Question:
MapRecord implements MutableRecord { @Override public boolean addField(String field, List<Value> values) { if (records.containsKey(field)) { return false; } records.put(field, values); return true; } MapRecord(); @Override List<Value> getValues(String field); @Override MutableRecord makeMutable(); @Override boolean isMutable(); @Override boolean addField(String field, List<Value> values); @Override boolean addValue(String field, Value value); @Override boolean removeField(String field); @Override boolean removeValue(String field, Value value); @Override boolean updateField(String field, List<Value> value); @Override boolean updateValue(String field, Value old_value, Value new_value); @Override boolean hasField(String field); @Override Set<String> getFields();  }### Answer:
@Test public void testAddField() { assertTrue(rec.addField("test", val)); assertFalse(rec.addField("test", val)); }