Test fails on CI only due to new lines

[dotherightthing]

/*
// Test fails on CI:
// due to new lines.
$this->assertEquals(
    '<div class="wpdtrt-anchorlinks__section wpdtrt-anchorlinks__anchor" id="heading-1" tabindex="-1"><h2 data-anchorlinks-id="heading-1">Heading 1<a class="wpdtrt-anchorlinks__anchor-link" href="#heading-1"><span aria-label="Anchor" class="wpdtrt-anchorlinks__anchor-icon">#</span></a></h2><p>Text</p></div>',
    trim( $dom->saveHTML( $dom->getElementsByTagName( 'div' )[0] ) ),
    'Expected first div to be a section containing a heading and text'
);
*/