I've experienced this failure locally. Steps to reproduce:
- Add a PHPUnit extensions which triggers the garbage collector (gc_collect_cycles()) after each test
- Run php tests/phpunit/phpunit.php tests/phpunit/languages/LanguageConverterTest.php
Very soon PHPUnit will print:
Language::__destruct() was not expected to be called. NULL
and the test suite will be killed without any additional information.
I'm checking whether this should be reported upstream.
Upstream issue: https://github.com/sebastianbergmann/phpunit/issues/4656