### Question:
FieldFilter { public void mapField(Bundle in, Bundle out) { ValueObject inVal = from.getValue(in); if (filter != null) { inVal = filter.filter(inVal, in); } if (inVal != null || toNull) { to.setValue(out, inVal); } } @SuppressWarnings("unused") private  FieldFilter(@JsonProperty(value = "from", required = true) AutoField from,
                        @JsonProperty(value = "to") AutoField to);  FieldFilter(String copyFieldName); void mapField(Bundle in, Bundle out);  }### Answer:
@Test public void mapField() throws Exception { FieldFilter fieldFilter = decodeObject(FieldFilter.class, "from: A, default: DEF"); Bundle fromBundle = decode("C: C_VAL"); Bundle toBundle = decode("D: D_VAL"); fieldFilter.mapField(fromBundle, toBundle); log.debug("toBundle: {}", toBundle); AutoField field = newAutoField("A"); assertEquals(decodeValue("DEF"), field.getValue(toBundle)); }