public void testGetInstantConverterRemovedNull() {
        try {
            ConverterManager.getInstance().removeInstantConverter(NullConverter.INSTANCE);
            try {
                ConverterManager.getInstance().getInstantConverter(null);
                fail();
            } catch (IllegalArgumentException ex) {}
        } finally {
            ConverterManager.getInstance().addInstantConverter(NullConverter.INSTANCE);
        }
        assertEquals(6, ConverterManager.getInstance().getInstantConverters().length);
    }