### Question:
SimpleStructConverter implements StructConverter { @Override public final byte[] convert(final Struct struct) { try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); DataOutputStream dataOutputStream = new DataOutputStream(byteArrayOutputStream)) { StructElements structElements = struct.getClass().getAnnotation(StructElements.class); if (structElements == null) { throw new StructConversionException(String.format( "%s does not have the proper @StructElements definition on the class " + "type. Please see documentation on Struct interface", struct.getClass().getSimpleName())); } for (String fieldName : structElements.elements()) { Field field = struct.getClass().getDeclaredField(fieldName); field.setAccessible(true); final Object value = FieldUtils.readField(field, struct); if (Struct.class.isAssignableFrom(field.getType())) { if (value == null) { continue; } dataOutputStream.write(convert((Struct) value)); } else if (int.class.isAssignableFrom(field.getType())) { dataOutputStream.writeInt((int) value); } else if (short.class.isAssignableFrom(field.getType())) { dataOutputStream.writeShort((short) value); } else if (byte[].class.isAssignableFrom(field.getType())) { dataOutputStream.write((byte[]) value); } else if (byte.class.isAssignableFrom(field.getType())) { dataOutputStream.writeByte((byte) value); } else { throw new StructConversionException( "Unsupported field type for element or length: " + field.getType()); } field.setAccessible(false); } dataOutputStream.flush(); return byteArrayOutputStream.toByteArray(); } catch (IOException | IllegalAccessException | NoSuchFieldException e) { throw new StructConversionException( String.format("Unexpected error converting %s into a struct: %s", struct.getClass().getSimpleName(), e.getMessage()), e); } }  @Override final byte[] convert(final Struct struct); @Override final T convert(final byte[] data, final Class<T> type);  }### Answer:
@Test public final void testConvertToByteArray() { byte[] serializedStruct = converter.convert(testStruct); Assert.assertEquals(serializedStruct, EXPECTED_BYTES); }
@Test public final void testConvertToStruct() { TestStruct struct = converter.convert(EXPECTED_BYTES, TestStruct.class); assert (struct.equals(testStruct)); }
@Test(expectedExceptions = StructConversionException.class, expectedExceptionsMessageRegExp = ".*@StructElements.*") public final void testNoElementsStructConvertToArray() { converter.convert(new TestNoElementsAnnotationStruct()); }
@Test(expectedExceptions = StructConversionException.class, expectedExceptionsMessageRegExp = ".*@StructElements.*") public final void testNoElementsStructConvertToStruct() { converter.convert(new byte[1], TestNoElementsAnnotationStruct.class); }
@Test(expectedExceptions = StructConversionException.class, expectedExceptionsMessageRegExp = "Unsupported field type.*") public final void testInvalidDataTypeStructConvertToArray() { converter.convert(new TestInvalidDataTypeStruct()); }
@Test(expectedExceptions = StructConversionException.class, expectedExceptionsMessageRegExp = "Unsupported field type.*") public final void testInvalidDataTypeStructConvertToStruct() { converter.convert(new byte[1], TestInvalidDataTypeStruct.class); }