@Override
    public Object convert(String value) {
        if (value == null || value.isEmpty()) {
            return value;
        }

        return value.toLowerCase(Locale.ENGLISH);
    }
@Test
    public void testConvert() throws Exception {
        Converter c = new LowercaseConverter(new HashMap<String, Object>());

        assertNull(c.convert(null));
        assertEquals("", c.convert(""));
        assertEquals("foobar", c.convert("foobar"));
        assertEquals("foo bar", c.convert("foo BAR"));
        assertEquals("foobar", c.convert("FooBar"));
        assertEquals("foobar ", c.convert("foobar "));
        assertEquals(" foobar", c.convert(" foobar"));
        assertEquals("foobar", c.convert("FOOBAR"));
    }