settings, region
<link rel="help" href="https://w3c.github.io/webvtt/#collect-webvtt-cue-timings-and-settings">

assert_equals(cues.length, 9);

var fooRegion = cues[0].region;
assert_true(!!fooRegion, 'Cue 0 has invalid region');

var barRegion = cues[1].region;
assert_true(!!barRegion, 'Cue 1 has invalid region');

assert_not_equals(fooRegion, barRegion);

var valid_regions = [
    fooRegion,
    barRegion,
    barRegion,
    null,
    fooRegion
];
valid_regions.forEach(function(valid, index) {
    assert_equals(cues[index].region, valid, 'Failed with cue ' + index);
});

for (var i = 0; i < 4; i++) {
    var index = valid_regions.length + i;

    assert_equals(cues[index].region, null);
}

===
WEBVTT

REGION
id:foo

REGION
id:bar

REGION
id:foo

REGION
width:10%

00:00:00.000 --> 00:00:01.000 region:foo
text0

00:00:00.000 --> 00:00:01.000 region:bar
text1

00:00:00.000 --> 00:00:01.000 region:foo region:bar
text2

00:00:00.000 --> 00:00:01.000 region:invalid
text3

00:00:00.000 --> 00:00:01.000 region:invalid region:foo
text4

00:00:00.000 --> 00:00:01.000 region:
invalid5

00:00:00.000 --> 00:00:01.000 region:\x20
invalid6

00:00:00.000 --> 00:00:01.000 region: foo
invalid7

00:00:00.000 --> 00:00:01.000 region :foo
invalid8