sebastianbergmann/comparator:5.0.2 can cause test failures in assertEqualsCanonicalizing()

sebastianbergmann/comparator:5.0.2 changed to way it processes arrays/objects in PHPUnits assertEqualsCanonicalizing().

It will now throw the failure below if the input isn't a list, so sequenced 0...n.

Drupal\Tests\system\Kernel\Common\UrlTest::testLinkBubbleableMetadata
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
 Array (
     'contexts' => Array (
         0 => 'languages:language_interface'
-        1 => 'session'
-        2 => 'theme'
-        3 => 'user.permissions'
+        1 => 'theme'
+        2 => 'user.permissions'
+        6 => 'session'
     )
     'tags' => []
     'max-age' => -1
 )

core/modules/system/tests/src/Kernel/Common/UrlTest.php:71

Note the values are the same for actual and expected but the keys of actual are not a list.

On encountering this test failure, you may attempt to overcome this by returning the array_values() of the method that causes the test-failure, since we're mostly only interested in the values anyway.

In core we did this for the following methods:
Cache::mergeTags() and Cache::mergeContexts() now return actual lists i.e. after removing dupes, the resulting array is sequenced 0...n.