It'd be really helpful if you explained how to run the test suite in there. I also thought you mentioned memory_limit=-1 and a bus error? The latter comes with segfault usually, which you can make with gdb: https://bugs.php.net/bugs-generating-backtrace.php

You can run that as:
gdb --args php `which phpunit`

And then "run" on the gdb prompt

The command I use to run the integration test suite is:

SYMFONY_DEPRECATIONS_HELPER=disabled CFP_ENV=testing vendor/bin/phpunit --testsuite integration

If I set memory_limit in my phpunit.xml file to be -1, it crashes with a bus error.

gdb has issues on macOS Catalina where it needs to be codesigned and I have tried numerous fixes to get it to work and have been unsuccessful.

Can't reproduce memory limit / bus error, presumably because the test suite does not work correctly: I get a lot of "RuntimeException: The config file "/home/nikic/repos/opencfp/config/testing.yml" does not exist" errors.

After creating a cfp_test mysql user and database and running "make integration" first, I now get:

Fatal error: Allowed memory size of 805306368 bytes exhausted at /home/nikic/php-7.4/Zend/zend_hash.c:2079 (tried to allocate 1048616 bytes) in /home/nikic/repos/opencfp/vendor/fzaninotto/faker/src/Faker/Provider/Text.php on line 84

I was not able to set memory_limit=-1 to produce the bus error, because the test runner apparently ignores ini files and options specified on the command line.

Turns out the memory_limit is set in the phpunit.xml.dist, and removing it there does produce a segfault. There is no useful trace because a corrupted function causes a jump to an invalid address. Unfortunately there are no warnings under valgrind.

My apologies for not providing clearer instructions for running the tests.

You could copy phpunit.xml.dist to phpunit.xml and change the memory_limit value in there, which the tests will then use.

Initial analysis suggests that this is caused by an RTD key collision. While a closure is being executed, the file that defines the closure is re-compiled and a colliding RTD key is generated, replacing the original closure. This is a long-standing problem without an easy fix, but we can at least mitigate this in a similar way we do for anon classes.

This likely also indicates a bug/inefficiency in Laravel, because it likely shouldn't be loading the same file twice.

[0x7fac0481b5d0] Illuminate\Database\Eloquent\Factory->load("/home/nikic/repos/opencfp/tests/../factories") /home/nikic/repos/opencfp/vendor/illuminate/database/Eloquent/Factory.php:202 
[0x7fac0481b500] Illuminate\Database\Eloquent\Factory->construct(object[0x7fac0481b550], "/home/nikic/repos/opencfp/tests/../factories") /home/nikic/repos/opencfp/vendor/illuminate/database/Eloquent/Factory.php:54 
[0x7fac0481b310] factory(object[0x7fac0481b360]) /home/nikic/repos/opencfp/tests/helpers.php:28 
[0x7fac0481b280] Illuminate\Database\Eloquent\Factory->{closure}() /home/nikic/repos/opencfp/factories/Common.php:36

Tests run through now with one failure that also exists on 7.3:

1) OpenCFP\Test\Integration\Http\Controller\Admin\SpeakersControllerTest::indexActionWorksCorrectly

Warning: sprintf(): Too few arguments in /home/nikic/repos/opencfp/vendor/codedungeon/phpunit-result-printer/src/ResultPrinter71.php on line 77

/home/nikic/repos/opencfp/tests/Helper/ResponseHelper.php:60
/home/nikic/repos/opencfp/tests/Integration/Http/Controller/Admin/SpeakersControllerTest.php:43

Reverted because it breaks ext/opcache/tests/bug65915.phpt.

Fixed in https://github.com/php/php-src/commit/0f2cdbf214efd98b4bdaf5ca41728faf00e7c037.