Excluding certain PHPUnit test groups results in "Database is dead" notice and tests terminate

[netweb]

When excluding certain PHPUnit groups from the full test suite the tests fail with a "Database is dead" notice.

Known groups thus far:

• phpunit --exclude-group import
• phpunit --exclude-group query

$ phpunit --exclude-group import
Installing...
Running as single site... To run multisite, use -c tests/phpunit/multisite.xml
PHPUnit 4.7.7 by Sebastian Bergmann and contributors.

.............................................................   61 / 4556 (  1%)
...................................SS........................  122 / 4556 (  2%)
.............................................................  183 / 4556 (  4%)
.............................................................  244 / 4556 (  5%)
.S...........................................................  305 / 4556 (  6%)
.............................................................  366 / 4556 (  8%)
.............................................................  427 / 4556 (  9%)
.............................................................  488 / 4556 ( 10%)
.............................................................  549 / 4556 ( 12%)
.............................................................  610 / 4556 ( 13%)
.....................S....S..................................  671 / 4556 ( 14%)
................................................S............  732 / 4556 ( 16%)
.............................................................  793 / 4556 ( 17%)
..................................Database is dead.

[netweb]

Adding another known case: phpunit --exclude-group xmlrpc

[isabel_brison]

I tested this using the test:php npm script, and found that the tests abort no matter what group I name after --exclude-group. Output is:

...........................................................    59 / 12551 (  0%)
...........................................................   118 / 12551 (  0%)
...............................EE..........................   177 / 12551 (  1%)
........................................EE...............E.   236 / 12551 (  1%)
.......FF.F.E.EE.FEFFFF....................................   295 / 12551 (  2%)
FEFF.FFFFF.EFEF.EFFFF.FFFF.FFF...EEEFEEEEEEEEEEEEEEEEEEEE.E   354 / 12551 (  2%)
EEFEEEEEEEEEEEEEEEEEEEE..FFFFFFS..FFFFF.FFFFF............-1% 

Specifying a --group works as expected.

Something else I noticed is that when passing --exclude-group, groups that are excluded by default, such as external-http, are no longer excluded. Not sure if that's related as those groups work fine when run individually.

[johnbillion]

I also saw this while working on #52645 and I'm pretty sure it's coming from a test in the ajax group.

## Summary

Preserves the default excluded PHPUnit groups when an additional --exclude-group argument is passed.

## Testing

• Run npm run test:php -- --filter Tests_PHPUnit_GroupFilters
• Run npm run test:php -- --exclude-group import --filter test_populate_site_meta
• Run npm run test:php -- --group ajax and verify ajax tests are no longer skipped by default

[arkaprabhachowdhury]

Opened [PR #11801](​https://github.com/WordPress/wordpress-develop/pull/11801) to address this ticket. Summary Preserves the default excluded PHPUnit groups when an additional --exclude-group argument is passed. Trac https://core.trac.wordpress.org/ticket/34185 Testing - Run npm run test:php -- --filter Tests_PHPUnit_GroupFilters - Run npm run test:php -- --exclude-group import --filter test_populate_site_meta - Run npm run test:php -- --group ajax and verify ajax tests are no longer skipped by default The PR includes focused regression coverage, and its validation details are recorded in the PR description.

I picked this up because the ticket describes a concrete core behavior or edge case that remains relevant in current WordPress. The proposed change is intentionally scoped to the ticket and is submitted here for code review, with the technical discussion remaining on this ticket.