### Question:
IF_UNUSED extends ISOFieldPackager { public int unpack (ISOComponent c, byte[] b, int offset) throws ISOException { throw new ISOException("IF_UNUSED: Packager should not unpack field " + c.getKey()); } IF_UNUSED(); byte[] pack(ISOComponent c); int unpack(ISOComponent c, byte[] b, int offset); int getMaxPackedLength();  }### Answer:
@Test public void testUnpack() throws Exception { byte[] raw = new byte[]{}; IF_UNUSED packager = new IF_UNUSED(); ISOField field = new ISOField(12); try { packager.unpack(field, raw, 0); fail("Should have thrown an exception"); } catch (Exception expected) { } }