Doctrine UUID data type: works perfect manually but fails in Codeception

Question

I'm building an Api Platform application in which User entity most likely has no email, username or any other human-readable identity. That is why I decided to use UUID-typed field as username ( User::getUsername() ). I installed ramsey/uuid-doctrine package and apply UUID Doctrine data type both for id property and uuid . Removed User::setUsername() method since we must assign it only once while creating new User instance. Now creating new User through API works perfect both in Swagger UI and manually with REST-client. But when I try to run simplest Codeception cest, executing $I->haveInRepository it throws

1) UserCest: Test creating user
 Test  tests/functional/UserCest.php:createUser

  [Doctrine\Common\Persistence\Mapping\MappingException] The class 'Ramsey\Uuid\Uuid' was not found in the chain configured namespaces App\Entity


Scenario Steps:

 1. $I->haveInRepository("App\\Entity\\User") at tests/functional/UserCest.php:17

#1  /Users/erop/Developer/temp/uuid-test/vendor/doctrine/persistence/lib/Doctrine/Common/Persistence/Mapping/MappingException.php:22
#2  /Users/erop/Developer/temp/uuid-test/vendor/doctrine/persistence/lib/Doctrine/Common/Persistence/Mapping/Driver/MappingDriverChain.php:87
#3  /Users/erop/Developer/temp/uuid-test/vendor/doctrine/orm/lib/Doctrine/ORM/Mapping/ClassMetadataFactory.php:151
#4  /Users/erop/Developer/temp/uuid-test/vendor/doctrine/persistence/lib/Doctrine/Common/Persistence/Mapping/AbstractClassMetadataFactory.php:304
#5  /Users/erop/Developer/temp/uuid-test/vendor/doctrine/orm/lib/Doctrine/ORM/Mapping/ClassMetadataFactory.php:78
#6  /Users/erop/Developer/temp/uuid-test/vendor/doctrine/persistence/lib/Doctrine/Common/Persistence/Mapping/AbstractClassMetadataFactory.php:183
#7  /Users/erop/Developer/temp/uuid-test/vendor/doctrine/orm/lib/Doctrine/ORM/EntityManager.php:283
#8  Codeception\Module\Doctrine2->haveInRepository
#9  /Users/erop/Developer/temp/uuid-test/tests/_support/_generated/FunctionalTesterActions.php:2792
#10 /Users/erop/Developer/temp/uuid-test/tests/functional/UserCest.php:17

Have no idea what and where should I tune up something to make test working. What I found on Internet mostly relate to relationship of entities in different bundles. But as you can see this is not the case. Any ideas how to fix the issue?