This is a testharness.js-based test.
[FAIL] container, item 1
assert_equals: \n<container data-expected-margin-top="10">\n <item data-expected-margin-top="0" class="collapsed">\n <item data-expected-margin-top="0" class="collapsed"></item>\n </item>\n <item data-expected-margin-top="0" style="margin-block: 40px">\n <item data-expected-margin-top="0" data-expected-margin-bottom="0" class="collapsed"></item>\n <item data-expected-margin-top="0" style="margin-top: 30px;">\n <item data-expected-margin-top="0" style="margin-block-start: 100px; height: 50px;"></item>\n </item>\n </item>\n </container>\nmargin-top expected "0" but got "50"
[FAIL] container, item 2
assert_equals: \n<item data-expected-margin-top="0" class="collapsed">\n <item data-expected-margin-top="0" class="collapsed"></item>\n </item>\nmargin-top expected "0" but got "50"
[FAIL] container, item 3
assert_equals: \n<item data-expected-margin-top="0" class="collapsed"></item>\nmargin-top expected "0" but got "50"
[FAIL] container, item 4
assert_equals: \n<item data-expected-margin-top="0" style="margin-block: 40px">\n <item data-expected-margin-top="0" data-expected-margin-bottom="0" class="collapsed"></item>\n <item data-expected-margin-top="0" style="margin-top: 30px;">\n <item data-expected-margin-top="0" style="margin-block-start: 100px; height: 50px;"></item>\n </item>\n </item>\nmargin-top expected "0" but got "40"
[FAIL] container, item 5
assert_equals: \n<item data-expected-margin-top="0" data-expected-margin-bottom="0" class="collapsed"></item>\nmargin-top expected "0" but got "40"
[FAIL] container, item 6
assert_equals: \n<item data-expected-margin-top="0" style="margin-top: 30px;">\n <item data-expected-margin-top="0" style="margin-block-start: 100px; height: 50px;"></item>\n </item>\nmargin-top expected "0" but got "40"
[FAIL] container, item 7
assert_equals: \n<item data-expected-margin-top="0" style="margin-block-start: 100px; height: 50px;"></item>\nmargin-top expected "0" but got "30"
Harness: the test ran to completion.