ComposerIntegrationTest and omposerValidateTest fail if run from a composer installed site

catch → credited slashrsm → .

Crediting @slashrsm who found the bug.

Maybe you could try a different command line from parent directory:
./vendor/bin/phpunit -c ./core ./modules/contrib/
or something like that, adapted to your directory structure.

I had the same errors (Composer not found) and what worked for me was ./vendor/bin/phpunit -c ./web/core ./web/modules/contrib/. I also added vendor/bin to my PATH but not sure it helped.

If it works that way then, maybe the online documentation → should be updated accordingly...

I'm running into the same issue with this:

./docker/bin/phpunit --colors=always \
	    -c /var/www/html/core/phpunit.xml.dist \
	    --testsuite=unit \
	    --group=$(PROFILE_NAME)

There were 2 PHPUnit errors:

1) Drupal\Tests\Composer\Generator\BuilderTest::testBuilder
The data provider specified for Drupal\Tests\Composer\Generator\BuilderTest::testBuilder is invalid
Class "Drupal\Composer\Composer" not found

/var/www/html/core/tests/Drupal/Tests/Composer/Generator/BuilderTest.php:91

2) Drupal\Tests\ComposerIntegrationTest::testComposerTilde
The data provider specified for Drupal\Tests\ComposerIntegrationTest::testComposerTilde is invalid
The "/var/www/html/composer" directory does not exist.

/var/www/html/core/tests/Drupal/Tests/ComposerIntegrationTest.php:55

The first error is looking for class Drupal\Composer\Composer, which would suggest composer is in the vendor/drupal/composer directory, but it's location in my project is actually vendor/composer/composer, so this should probably be changed to:

use Composer/Composer;

Ok think I found the issue. For some reason, composer is not bringing in the /composer directory from core, still troubleshooting why.

Ok figured out the issue with my tests, a bit confusing.

I thought this was drupal/core: https://git.drupalcode.org/project/drupal/-/tree/11.1.x?ref_type=heads

But the composer.json in the root of this repo is drupal/drupal. There is another composer.json file in /core, and that's drupal/core. So when we are requiring drupal/core-recommended, that requires drupal/core, and so the other files/directories in the root of that repo are not included.

To fix the issue, I added drupal/drupal to require-dev. This puts drupal/drupal in the vendor directory. I then use a composer post install/update script to move vendor/drupal/drupal/composer/* into html/composer (only if it exists with require-dev).

"scripts": {
        "post-install-cmd": [
            "@copy-composer-directory"
        ],
        "post-update-cmd": [
            "@copy-composer-directory"
        ],
        "copy-composer-directory": [
            "[ -d vendor/drupal/drupal/composer ] && mkdir -p html/composer && cp -R vendor/drupal/drupal/composer/* html/composer/ || echo 'composer directory not found; skipping copy'"
        ],
}

Now the Drupal\Tests\Composer\Generator\BuilderTest class, which requires the /composer directory to be in place, can access the proper drupal verison of composer with the Composer::drupalVersionBranch() method, which is obviously drupal specific.