There was 1 failure:

1) core_dml_testcase::test_coalesce

Failed asserting that null is identical to ''.

/home/fred/www/repositories/im_oracle/moodle/lib/dml/tests/dml_test.php:3785

/home/fred/www/repositories/im_oracle/moodle/lib/phpunit/classes/database_driver_testcase.php:143

To re-run:

 vendor/bin/phpunit core_dml_testcase lib/dml/tests/dml_test.php

Eloy says:

We used to have $DB->sql_empty() but was deprecated in favor of passing any empty string as parameter.
So, IMO that test is wrong and it should be passing parameters. But that is exactly tested by the next assertion (#3787). So I'd propose to, simply, get rid of that problematic assertion.
That or we revive (un-deprecate) $DB->sql_empty().