public URL convert(String value) {
        if (isBlank(value)) {
            throw new ParameterException(getErrorString("a blank value", "a valid URL"));
        }

        try {
            return URLUtil.parseURL(value);
        } catch (IllegalArgumentException e) {
            throw new ParameterException(getErrorString(value, "a valid URL"));
        }

    }
@Test
    public void urlIsCreatedFromFileUrl() {
        URL url = converter.convert("file:/path/to/something");

        assertThat(url.toString(), is("file:/path/to/something"));
    }