Small details.

tests/phpunit/tests/html-api/wpHtmlTagProcessor-bookmark.php

@@ -308,7 +308,11 @@ public function test_updates_bookmark_for_additions_after_both_sides() {
 		$processor->seek( 'first' );
 		$processor->add_class( 'first' );
 
-		$this->assertSame( 'one', $processor->get_attribute( 'id' ) );
+		$this->assertSame(
+			'one',
+			$processor->get_attribute( 'id' ),
+			'Should have remembered attribute change from before the seek.'
+		);
 
 		$this->assertSame(
 			'<div class="first" id="one">First</div><div class="second" id="two">Second</div>',

tests/phpunit/tests/html-api/wpHtmlTagProcessor.php

@@ -2759,15 +2759,17 @@ public function insert_after( $new_html ) {
 		$subclass->next_tag();
 		$this->assertSame(
 			'P',
-			$subclass->get_tag()
+			$subclass->get_tag(),
+			'Should have matched inserted HTML as next tag.'
 		);
 
 		$subclass->next_tag( 'img' );
 		$subclass->set_attribute( 'alt', 'mountain' );
 
 		$this->assertSame(
 			'<div><img><p>snow-capped</p></div><div><img alt="mountain"></div>',
-			$subclass->get_updated_html()
+			$subclass->get_updated_html(),
+			'Should have properly applied the update from in front of the cursor.'
 		);
 	}
 }