@Test
public void canParseAnyFilenameThatStartsWithANumber() throws Exception {

	FilenameParser parser = new FilenameParser();
	assertEquals(1L, parser.extractIdFromFilename("0001_a_filename.txt"));
	assertEquals(1L, parser.extractIdFromFilename("1_a_filename.txt"));
	assertEquals(1L, parser.extractIdFromFilename("1 a filename.txt"));
	assertEquals(1L, parser.extractIdFromFilename("1.txt"));
	assertEquals(123L, parser.extractIdFromFilename("00123_something.txt"));
}