t/as_html.t and t/replace_with.t fail on some systems

[eserte]

On some of my smokers I see the following failures:

#   Failed test 'html() on unbound nodes'
#   at t/as_html.t line 22.
#          got: ''
#     expected: 'Hi there'
# Looks like you failed 1 test of 4.
t/as_html.t ........ 
Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/4 subtests 
...
#   Failed test 'return removed'
#   at t/replace_with.t line 14.
#          got: ''
#     expected: '<div class="second"/>'
# Looks like you failed 1 test of 12.
t/replace_with.t ... 
Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/12 subtests 

Reason is unknown. It seems that it depends on the operating system: newer ones (e.g. debian 12, freebsd 13..15) are affected, some older (debian 10..11) are not.