    @Test
    public void testConvert() throws Exception {

        System.out.println("convert");
        StringField instance;

        instance = new StringField(Types.STRING, "36");
        UUID expectedResult = UUID.randomUUID();
        assertEquals(expectedResult.toString(), instance.convert(expectedResult));
        assertEquals(expectedResult.toString(), instance.convert(expectedResult.toString()));

        instance = new StringField(Types.STRING, "35");
        try {
            instance.convert(expectedResult.toString());
            fail("StringField failed to do constraint check");
        } catch (OperationException ex) {
            assertEquals(ErrorCode.DATATYPE_CONSTRAINT_VIOLATION, ex.getErrorCode());
        }
    }