### Question:
ISOFieldPackager { public abstract int unpack (ISOComponent c, byte[] b, int offset) throws ISOException; ISOFieldPackager();  ISOFieldPackager(int len, String description); String getDescription(); void setDescription(String description); int getLength(); void setLength(int len); void setPad(boolean pad); void setTrim(boolean trim); abstract int getMaxPackedLength(); ISOComponent createComponent(int fieldNumber); abstract byte[] pack(ISOComponent c); abstract int unpack(ISOComponent c, byte[] b, int offset); void unpack(ISOComponent c, InputStream in); void pack(ISOComponent c, ObjectOutput out);  }### Answer:
@SuppressWarnings("deprecation") @Test public void testUnpack() throws Throwable { ISOComponent c = new ISOField(); ISOFieldPackager iF_ECHAR = new IF_ECHAR(100, "testISOFieldPackagerDescription"); byte[] bytes = new byte[0]; iF_ECHAR.setLength(0); iF_ECHAR.unpack(c, new ByteArrayInputStream(bytes)); assertEquals("", ((ISOField) c).value, "(ISOVField) c.value"); }
@Test public void testUnpackThrowsArrayIndexOutOfBoundsException() throws Throwable { byte[] bytes = new byte[2]; InputStream in = new ByteArrayInputStream(bytes); try { new IFEB_LLLNUM().unpack(new ISOMsg("testISOFieldPackagerMti"), in); fail("Expected ArrayIndexOutOfBoundsException to be thrown"); } catch (ArrayIndexOutOfBoundsException ex) { if (isJavaVersionAtMost(JAVA_10)) { assertEquals("2", ex.getMessage(), "ex.getMessage()"); } else { assertEquals("Index 2 out of bounds for length 2", ex.getMessage(), "ex.getMessage()"); } assertEquals(0, in.available(), "(ByteArrayInputStream) in.available()"); } }