It might be interesting to test a greater range of characters using the provider functionality of PHPUnit

````php
public function provideTestOutOfRangeCharacters()
{
    return array(
        array(urldecode('%01%02%03%00'), false),
        array('This is valid', true),
        // etc
    );
}

/**
 * @dataProvider provideTestOutOfRangeCharacters
 */
public function testOutOfRangeCharacters($string, $isValid)
{
    if (false === $isValid) {
        $this->setExpectedException('PHPCR\ValueFormatException', 'Invalid character'); // second argument matches partially against exception message
    }

    ...
}
`````

If that makes sense.