hibernate.mapping.default_list_semantics (`AvailableSettings#DEFAULT_LIST_SEMANTICS`)

make LIST the default classification for List attributes with no `@OrderColumn`, etc.

documentation/src/test/java/org/hibernate/userguide/associations/ManyToManyBidirectionalTest.java

@@ -8,6 +8,7 @@ package org.hibernate.userguide.associations;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import jakarta.persistence.CascadeType;
 import jakarta.persistence.Column;
@@ -17,10 +18,12 @@ import jakarta.persistence.Id;
 import jakarta.persistence.ManyToMany;
 
 import org.hibernate.annotations.NaturalId;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 
 /**
@@ -36,6 +39,12 @@ public class ManyToManyBidirectionalTest extends BaseEntityManagerFunctionalTest
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void testLifecycle() {
 		doInJPA(this::entityManagerFactory, entityManager -> {

documentation/src/test/java/org/hibernate/userguide/collections/OrderedBySQLTest.java

@@ -8,6 +8,8 @@ package org.hibernate.userguide.collections;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.CascadeType;
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;
@@ -17,11 +19,13 @@ import jakarta.persistence.ManyToOne;
 import jakarta.persistence.OneToMany;
 
 import org.hibernate.dialect.H2Dialect;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.hibernate.testing.RequiresDialect;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 
@@ -39,6 +43,12 @@ public class OrderedBySQLTest extends BaseEntityManagerFunctionalTestCase {
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void testLifecycle() {
 		doInJPA(this::entityManagerFactory, entityManager -> {

documentation/src/test/java/org/hibernate/userguide/fetching/FetchModeJoinTest.java

@@ -8,6 +8,8 @@ package org.hibernate.userguide.fetching;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;
 import jakarta.persistence.GeneratedValue;
@@ -18,10 +20,12 @@ import jakarta.persistence.OneToMany;
 import org.hibernate.annotations.Fetch;
 import org.hibernate.annotations.FetchMode;
 import org.hibernate.annotations.NaturalId;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 
@@ -38,6 +42,12 @@ public class FetchModeJoinTest extends BaseEntityManagerFunctionalTestCase {
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void test() {
 		doInJPA(this::entityManagerFactory, entityManager -> {

documentation/src/test/java/org/hibernate/userguide/fetching/FetchModeSelectTest.java

@@ -8,6 +8,8 @@ package org.hibernate.userguide.fetching;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;
 import jakarta.persistence.GeneratedValue;
@@ -18,10 +20,12 @@ import jakarta.persistence.OneToMany;
 import org.hibernate.annotations.Fetch;
 import org.hibernate.annotations.FetchMode;
 import org.hibernate.annotations.NaturalId;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 
@@ -38,6 +42,12 @@ public class FetchModeSelectTest extends BaseEntityManagerFunctionalTestCase {
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void test() {
 		doInJPA(this::entityManagerFactory, entityManager -> {

documentation/src/test/java/org/hibernate/userguide/fetching/FetchModeSubselectTest.java

@@ -8,6 +8,8 @@ package org.hibernate.userguide.fetching;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;
 import jakarta.persistence.GeneratedValue;
@@ -18,10 +20,12 @@ import jakarta.persistence.OneToMany;
 import org.hibernate.annotations.Fetch;
 import org.hibernate.annotations.FetchMode;
 import org.hibernate.annotations.NaturalId;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 
@@ -38,6 +42,12 @@ public class FetchModeSubselectTest extends BaseEntityManagerFunctionalTestCase
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void test() {
 		doInJPA(this::entityManagerFactory, entityManager -> {

documentation/src/test/java/org/hibernate/userguide/fetching/GraphFetchingTest.java

@@ -9,6 +9,8 @@ package org.hibernate.userguide.fetching;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;
@@ -24,11 +26,13 @@ import jakarta.persistence.QueryHint;
 import org.hibernate.annotations.ColumnTransformer;
 import org.hibernate.annotations.NaturalId;
 import org.hibernate.dialect.H2Dialect;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.hibernate.testing.RequiresDialect;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
@@ -49,6 +53,12 @@ public class GraphFetchingTest extends BaseEntityManagerFunctionalTestCase {
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void test() {
 		doInJPA(this::entityManagerFactory, entityManager -> {

documentation/src/test/java/org/hibernate/userguide/pc/FilterTest.java

@@ -8,6 +8,8 @@ package org.hibernate.userguide.pc;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.CascadeType;
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
@@ -24,10 +26,12 @@ import org.hibernate.Session;
 import org.hibernate.annotations.Filter;
 import org.hibernate.annotations.FilterDef;
 import org.hibernate.annotations.ParamDef;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -47,6 +51,12 @@ public class FilterTest extends BaseEntityManagerFunctionalTestCase {
         };
     }
 
+    @Override
+    protected void addConfigOptions(Map options) {
+        super.addConfigOptions( options );
+        options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+    }
+
     @Test
     public void testLifecycle() {
         doInJPA(this::entityManagerFactory, entityManager -> {

documentation/src/test/java/org/hibernate/userguide/pc/PersistenceContextTest.java

@@ -9,6 +9,7 @@ package org.hibernate.userguide.pc;
 import java.sql.Statement;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import jakarta.persistence.CascadeType;
 import jakarta.persistence.Entity;
@@ -26,10 +27,12 @@ import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.annotations.NaturalId;
 import org.hibernate.engine.spi.SessionImplementor;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
@@ -48,6 +51,12 @@ public class PersistenceContextTest extends BaseEntityManagerFunctionalTestCase
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void test() {
 		doInJPA(this::entityManagerFactory, entityManager -> {

documentation/src/test/java/org/hibernate/userguide/pc/WhereJoinTableTest.java

@@ -9,6 +9,8 @@ package org.hibernate.userguide.pc;
 import java.sql.Statement;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.Entity;
 import jakarta.persistence.Id;
 import jakarta.persistence.JoinColumn;
@@ -18,11 +20,13 @@ import jakarta.persistence.ManyToMany;
 import org.hibernate.Session;
 import org.hibernate.annotations.WhereJoinTable;
 import org.hibernate.dialect.H2Dialect;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.hibernate.testing.RequiresDialect;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 
@@ -40,6 +44,12 @@ public class WhereJoinTableTest extends BaseEntityManagerFunctionalTestCase {
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void testLifecycle() {
 		//tag::pc-where-persistence-example[]

documentation/src/test/java/org/hibernate/userguide/pc/WhereTest.java

@@ -8,6 +8,8 @@ package org.hibernate.userguide.pc;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
 import jakarta.persistence.EnumType;
@@ -17,10 +19,12 @@ import jakarta.persistence.ManyToOne;
 import jakarta.persistence.OneToMany;
 
 import org.hibernate.annotations.Where;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 
@@ -37,6 +41,12 @@ public class WhereTest extends BaseEntityManagerFunctionalTestCase {
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void testLifecycle() {
 		//tag::pc-where-persistence-example[]

documentation/src/test/java/org/hibernate/userguide/sql/CollectionLoaderTest.java

@@ -10,6 +10,8 @@ import java.sql.Statement;
 import java.sql.Types;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.ElementCollection;
 import jakarta.persistence.Entity;
 import jakarta.persistence.GeneratedValue;
@@ -26,6 +28,7 @@ import org.hibernate.annotations.SQLInsert;
 import org.hibernate.annotations.SQLUpdate;
 import org.hibernate.dialect.H2Dialect;
 import org.hibernate.dialect.PostgreSQLDialect;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.hibernate.testing.RequiresDialect;
@@ -33,6 +36,7 @@ import org.hibernate.testing.TestForIssue;
 import org.junit.Before;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 
@@ -52,6 +56,12 @@ public class CollectionLoaderTest extends BaseEntityManagerFunctionalTestCase {
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Before
 	public void init() {
 		doInJPA(this::entityManagerFactory, entityManager -> {

documentation/src/test/java/org/hibernate/userguide/sql/CustomSQLTest.java

@@ -9,6 +9,8 @@ package org.hibernate.userguide.sql;
 import java.sql.Statement;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.ElementCollection;
 import jakarta.persistence.Entity;
 import jakarta.persistence.GeneratedValue;
@@ -26,12 +28,14 @@ import org.hibernate.annotations.SQLUpdate;
 import org.hibernate.annotations.Where;
 import org.hibernate.dialect.H2Dialect;
 import org.hibernate.dialect.PostgreSQLDialect;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 
 import org.hibernate.testing.RequiresDialect;
 import org.junit.Before;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
@@ -50,6 +54,12 @@ public class CustomSQLTest extends BaseEntityManagerFunctionalTestCase {
 		};
 	}
 
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Before
 	public void init() {
 		doInJPA(this::entityManagerFactory, entityManager -> {

hibernate-core/src/main/java/org/hibernate/boot/internal/MetadataBuilderImpl.java

@@ -476,8 +476,7 @@ public class MetadataBuilderImpl implements MetadataBuilderImplementor, TypeCont
 						}
 						return classification;
 					},
-					// for now, to follow legacy behavior
+					CollectionClassification.LIST
-					CollectionClassification.BAG
 			);
 		}
 

hibernate-core/src/test/java/org/hibernate/orm/test/annotations/derivedidentities/bidirectional/CompositeIdDerivedIdWithIdClassTest.java

@@ -15,8 +15,11 @@ import org.hibernate.jpa.internal.PersistenceUnitUtilImpl;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 
@@ -29,11 +32,21 @@ import jakarta.persistence.JoinColumn;
 import jakarta.persistence.ManyToOne;
 import jakarta.persistence.OneToMany;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+/**
+ * @author Andrea Boriero
+ */
+@ServiceRegistry(
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class
+		)
+)
 @DomainModel(
 		annotatedClasses = {
 				CompositeIdDerivedIdWithIdClassTest.ShoppingCart.class,

hibernate-core/src/test/java/org/hibernate/orm/test/annotations/index/jpa/AbstractJPAIndexTest.java

@@ -10,6 +10,8 @@ import java.util.Iterator;
 
 import org.hibernate.boot.MetadataBuilder;
 import org.hibernate.boot.model.naming.ImplicitNamingStrategyJpaCompliantImpl;
+import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+import org.hibernate.cfg.AvailableSettings;
 import org.hibernate.internal.util.StringHelper;
 import org.hibernate.mapping.Bag;
 import org.hibernate.mapping.Column;
@@ -20,6 +22,7 @@ import org.hibernate.mapping.Property;
 import org.hibernate.mapping.Set;
 import org.hibernate.mapping.Table;
 import org.hibernate.mapping.UniqueKey;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.junit4.BaseNonConfigCoreFunctionalTestCase;
 import org.junit.Test;
@@ -39,6 +42,12 @@ public abstract class AbstractJPAIndexTest extends BaseNonConfigCoreFunctionalTe
 		metadataBuilder.applyImplicitNamingStrategy( ImplicitNamingStrategyJpaCompliantImpl.INSTANCE );
 	}
 
+	@Override
+	protected void configureStandardServiceRegistryBuilder(StandardServiceRegistryBuilder ssrb) {
+		super.configureStandardServiceRegistryBuilder( ssrb );
+		ssrb.applySetting( AvailableSettings.DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG );
+	}
+
 	@Test
 	public void testTableIndex() {
 		PersistentClass entity = metadata().getEntityBinding( Car.class.getName() );

hibernate-core/src/test/java/org/hibernate/orm/test/annotations/manytomany/ManyToManyTest.java

@@ -23,7 +23,9 @@ import jakarta.persistence.criteria.Root;
 import org.hibernate.Hibernate;
 import org.hibernate.Session;
 import org.hibernate.Transaction;
+import org.hibernate.cfg.AvailableSettings;
 import org.hibernate.cfg.Configuration;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
@@ -45,6 +47,7 @@ public class ManyToManyTest extends BaseCoreFunctionalTestCase {
 	@Override
 	protected void configure(Configuration configuration) {
 		super.configure( configuration );
+		configuration.setProperty( AvailableSettings.DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
 //		configuration.setImplicitNamingStrategy( ImplicitNamingStrategyJpaCompliantImpl.INSTANCE );
 	}
 

hibernate-core/src/test/java/org/hibernate/orm/test/annotations/onetomany/OneToManyTest.java

@@ -12,6 +12,7 @@ import java.util.Collections;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.SortedSet;
 import java.util.TreeSet;
@@ -36,6 +37,7 @@ import org.hibernate.exception.ConstraintViolationException;
 import org.hibernate.mapping.Column;
 import org.hibernate.mapping.PersistentClass;
 import org.hibernate.mapping.Table;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.DialectChecks;
 import org.hibernate.testing.RequiresDialectFeature;
@@ -49,6 +51,7 @@ import org.hibernate.test.annotations.TicketComparator;
 import org.junit.Assert;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.junit4.ExtraAssertions.assertTyping;
 import static org.hibernate.testing.transaction.TransactionUtil.doInHibernate;
 import static org.junit.Assert.assertEquals;
@@ -570,6 +573,13 @@ public class OneToManyTest extends BaseNonConfigCoreFunctionalTestCase {
 		return new String[] { "org/hibernate/orm/test/annotations/onetomany/orm.xml" };
 	}
 
+	@Override
+	protected void addSettings(Map settings) {
+		super.addSettings( settings );
+		// needed for `#testListWithBagSemanticAndOrderBy`
+		settings.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Entity(name = "OnDeleteUnidirectionalOneToManyParent")
 	@jakarta.persistence.Table(name = "OneToManyParent")
 	public static class OnDeleteUnidirectionalOneToManyParent {

hibernate-core/src/test/java/org/hibernate/orm/test/annotations/onetomany/OrderByTest.java

@@ -6,6 +6,7 @@
  */
 package org.hibernate.orm.test.annotations.onetomany;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
@@ -30,6 +31,7 @@ import org.hibernate.dialect.OracleDialect;
 import org.hibernate.dialect.SQLServerDialect;
 import org.hibernate.engine.spi.SessionImplementor;
 import org.hibernate.graph.RootGraph;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.persister.collection.CollectionPersister;
 import org.hibernate.persister.collection.QueryableCollection;
 import org.hibernate.query.Query;
@@ -500,6 +502,7 @@ public class OrderByTest extends BaseCoreFunctionalTestCase {
 	@Override
 	protected void configure(Configuration configuration) {
 		configuration.setProperty( AvailableSettings.DEFAULT_NULL_ORDERING, "last" );
+		configuration.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
 	}
 
 	@Override

hibernate-core/src/test/java/org/hibernate/orm/test/batchfetch/BatchFetchReferencedColumnNameTest.java

@@ -13,10 +13,12 @@ import org.hibernate.cfg.AvailableSettings;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
 import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
 import org.hibernate.testing.orm.junit.Setting;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.junit.jupiter.api.Test;
 
 import jakarta.persistence.CascadeType;
@@ -29,6 +31,7 @@ import jakarta.persistence.OneToMany;
 import jakarta.persistence.OrderBy;
 import jakarta.persistence.Table;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 
@@ -45,7 +48,11 @@ import static org.junit.jupiter.api.Assertions.assertNotNull;
 				@Setting(name = AvailableSettings.SHOW_SQL, value = "true"),
 				@Setting(name = AvailableSettings.FORMAT_SQL, value = "true"),
 				@Setting(name = AvailableSettings.DEFAULT_BATCH_FETCH_SIZE, value = "64")
-		}
+		},
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class
+		)
 )
 public class BatchFetchReferencedColumnNameTest {
 

hibernate-core/src/test/java/org/hibernate/orm/test/bytecode/enhancement/lazy/LazyLoadingIntegrationTest.java

@@ -10,6 +10,7 @@ import org.hibernate.annotations.LazyToOne;
 import org.hibernate.annotations.LazyToOneOption;
 import org.hibernate.cfg.AvailableSettings;
 import org.hibernate.cfg.Configuration;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.bytecode.enhancement.BytecodeEnhancerRunner;
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
@@ -30,6 +31,7 @@ import jakarta.persistence.Table;
 import java.util.ArrayList;
 import java.util.List;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.bytecode.enhancement.EnhancerTestUtils.checkDirtyTracking;
 import static org.hibernate.testing.transaction.TransactionUtil.doInHibernate;
 
@@ -51,6 +53,7 @@ public class LazyLoadingIntegrationTest extends BaseCoreFunctionalTestCase {
     protected void configure(Configuration configuration) {
         configuration.setProperty( AvailableSettings.USE_SECOND_LEVEL_CACHE, "false" );
         configuration.setProperty( AvailableSettings.ENABLE_LAZY_LOAD_NO_TRANS, "true" );
+        configuration.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
     }
 
     @Before

hibernate-core/src/test/java/org/hibernate/orm/test/bytecode/enhancement/lazy/proxy/BytecodeEnhancedLazyLoadingOnDeletedEntityTest.java

@@ -7,10 +7,13 @@
 package org.hibernate.orm.test.bytecode.enhancement.lazy.proxy;
 
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInHibernate;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
+
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;
 import jakarta.persistence.Id;
@@ -18,6 +21,7 @@ import jakarta.persistence.ManyToMany;
 import jakarta.persistence.Table;
 
 import org.hibernate.LazyInitializationException;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.bytecode.enhancement.BytecodeEnhancerRunner;
@@ -38,6 +42,12 @@ public class BytecodeEnhancedLazyLoadingOnDeletedEntityTest
 		return new Class<?>[] { AssociationOwner.class, AssociationNonOwner.class };
 	}
 
+	@Override
+	protected void addSettings(Map settings) {
+		super.addSettings( settings );
+		settings.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@After
 	public void tearDown() {
 		doInHibernate( this::sessionFactory, s -> {

hibernate-core/src/test/java/org/hibernate/orm/test/cache/CollectionCacheEvictionTest.java

@@ -13,6 +13,7 @@ import org.hibernate.cache.spi.access.CollectionDataAccess;
 import org.hibernate.cfg.Configuration;
 import org.hibernate.cfg.Environment;
 import org.hibernate.engine.spi.SessionImplementor;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.persister.collection.CollectionPersister;
 
 import org.hibernate.testing.TestForIssue;
@@ -21,6 +22,7 @@ import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
@@ -53,6 +55,7 @@ public class CollectionCacheEvictionTest extends BaseCoreFunctionalTestCase {
 		cfg.setProperty( Environment.USE_SECOND_LEVEL_CACHE, "true" );
 		cfg.setProperty( Environment.USE_QUERY_CACHE, "true" );
 		cfg.setProperty( Environment.CACHE_PROVIDER_CONFIG, "true" );
+		cfg.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
 	}
 
 	@Override

hibernate-core/src/test/java/org/hibernate/orm/test/cache/LockModeTest.java

@@ -9,10 +9,12 @@ import org.hibernate.Session;
 import org.hibernate.cache.internal.CollectionCacheInvalidator;
 import org.hibernate.cfg.Configuration;
 import org.hibernate.cfg.Environment;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
@@ -45,6 +47,7 @@ public class LockModeTest extends BaseCoreFunctionalTestCase {
 		cfg.setProperty( Environment.USE_SECOND_LEVEL_CACHE, "true" );
 		cfg.setProperty( Environment.USE_QUERY_CACHE, "true" );
 		cfg.setProperty( Environment.CACHE_PROVIDER_CONFIG, "true" );
+		cfg.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
 	}
 
 	@Override

hibernate-core/src/test/java/org/hibernate/orm/test/cache/ManyToManyCollectionCacheEvictionTest.java

@@ -15,12 +15,14 @@ import org.hibernate.annotations.CacheConcurrencyStrategy;
 import org.hibernate.cache.internal.CollectionCacheInvalidator;
 import org.hibernate.cfg.Configuration;
 import org.hibernate.cfg.Environment;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.Assert.assertEquals;
 
 /**
@@ -49,6 +51,7 @@ public class ManyToManyCollectionCacheEvictionTest extends BaseCoreFunctionalTes
 		cfg.setProperty( Environment.USE_SECOND_LEVEL_CACHE, "true" );
 		cfg.setProperty( Environment.USE_QUERY_CACHE, "true" );
 		cfg.setProperty( Environment.CACHE_PROVIDER_CONFIG, "true" );
+		cfg.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
 	}
 
 	@Test

hibernate-core/src/test/java/org/hibernate/orm/test/collection/bag/BagElementNullBasicTest.java

@@ -8,6 +8,9 @@ package org.hibernate.orm.test.collection.bag;
 
 import java.util.ArrayList;
 import java.util.List;
+
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
+
 import jakarta.persistence.CollectionTable;
 import jakarta.persistence.Column;
 import jakarta.persistence.ElementCollection;
@@ -20,16 +23,24 @@ import jakarta.persistence.Table;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.junit.jupiter.api.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 
 /**
  * @author Gail Badner
  */
+@ServiceRegistry(
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class )
+)
 @DomainModel(annotatedClasses = {
 		BagElementNullBasicTest.AnEntity.class,
 		BagElementNullBasicTest.NullableElementsEntity.class

hibernate-core/src/test/java/org/hibernate/orm/test/collection/bag/MultipleBagFetchHqlTest.java

@@ -18,17 +18,26 @@ import jakarta.persistence.OneToMany;
 import jakarta.persistence.Table;
 
 import org.hibernate.loader.MultipleBagFetchException;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
 
 import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
 
+@ServiceRegistry(
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class )
+)
 @DomainModel(
 		annotatedClasses = {
 				MultipleBagFetchHqlTest.Post.class,

hibernate-core/src/test/java/org/hibernate/orm/test/collection/delayedOperation/DetachedBagDelayedOperationTest.java

@@ -24,6 +24,7 @@ import jakarta.persistence.OneToMany;
 
 import org.hibernate.Hibernate;
 import org.hibernate.collection.spi.AbstractPersistentCollection;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
 import org.hibernate.type.CollectionType;
 
 import org.hibernate.testing.TestForIssue;
@@ -31,12 +32,15 @@ import org.hibernate.testing.orm.junit.DomainModel;
 import org.hibernate.testing.orm.junit.LoggingInspections;
 import org.hibernate.testing.orm.junit.LoggingInspectionsScope;
 import org.hibernate.testing.orm.junit.MessageKeyWatcher;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -47,6 +51,11 @@ import static org.junit.jupiter.api.Assertions.fail;
  *
  * @author Gail Badner
  */
+@ServiceRegistry(
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class )
+)
 @DomainModel(
 		annotatedClasses = {
 				DetachedBagDelayedOperationTest.Parent.class,

hibernate-core/src/test/java/org/hibernate/orm/test/ecid/EmbeddedIdWithMapsIdTargetingDerivedEntityTest.java

@@ -12,8 +12,11 @@ import java.util.List;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.junit.jupiter.api.Test;
 
 import jakarta.persistence.Column;
@@ -30,6 +33,7 @@ import jakarta.persistence.OneToMany;
 import jakarta.persistence.Table;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.orm.test.util.SchemaUtil.getColumnNames;
 
 /**
@@ -58,6 +62,12 @@ import static org.hibernate.orm.test.util.SchemaUtil.getColumnNames;
  * at org.hibernate.testing.junit4.TestClassMetadata.performCallbackInvocation(TestClassMetadata.java:205)
  */
 @TestForIssue(jiraKey = "HHH-13295")
+@ServiceRegistry(
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class
+		)
+)
 @DomainModel(
 		annotatedClasses = {
 				EmbeddedIdWithMapsIdTargetingDerivedEntityTest.Attendance.class,

hibernate-core/src/test/java/org/hibernate/orm/test/embeddable/OrderByEmbeddableToOneTest.java

@@ -17,12 +17,15 @@ import jakarta.persistence.ManyToOne;
 import jakarta.persistence.OrderBy;
 
 import org.hibernate.Session;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.query.Query;
 
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
 import org.junit.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 
 public class OrderByEmbeddableToOneTest extends BaseCoreFunctionalTestCase {
 
@@ -31,6 +34,12 @@ public class OrderByEmbeddableToOneTest extends BaseCoreFunctionalTestCase {
 		return new Class[] { Containing.class, Embed.class, Contained.class };
 	}
 
+	@Override
+	protected void configure(Configuration configuration) {
+		super.configure( configuration );
+		configuration.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void test() {
 		inTransaction( session -> {

hibernate-core/src/test/java/org/hibernate/orm/test/embeddable/OrderByEmbeddableX2Test.java

@@ -17,12 +17,15 @@ import jakarta.persistence.Id;
 import jakarta.persistence.OrderBy;
 
 import org.hibernate.Session;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.query.Query;
 
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
 import org.junit.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 
 public class OrderByEmbeddableX2Test extends BaseCoreFunctionalTestCase {
 
@@ -31,6 +34,12 @@ public class OrderByEmbeddableX2Test extends BaseCoreFunctionalTestCase {
 		return new Class[] { Containing.class, Embed.class, Contained.class };
 	}
 
+	@Override
+	protected void configure(Configuration configuration) {
+		super.configure( configuration );
+		configuration.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void test() {
 		inTransaction( session -> {

hibernate-core/src/test/java/org/hibernate/orm/test/event/collection/detached/BadMergeHandlingTest.java

@@ -11,11 +11,13 @@ import java.util.List;
 import org.hibernate.Session;
 import org.hibernate.boot.model.naming.ImplicitNamingStrategyLegacyJpaImpl;
 import org.hibernate.cfg.Configuration;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.Assert.assertEquals;
 
 /**
@@ -27,6 +29,7 @@ public class BadMergeHandlingTest extends BaseCoreFunctionalTestCase {
 	protected void configure(Configuration configuration) {
 		super.configure( configuration );
 		configuration.setImplicitNamingStrategy( ImplicitNamingStrategyLegacyJpaImpl.INSTANCE );
+		configuration.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
 	}
 
 	@Override

hibernate-core/src/test/java/org/hibernate/orm/test/event/collection/detached/MergeCollectionEventTest.java

@@ -20,12 +20,14 @@ import org.hibernate.event.spi.PostCollectionUpdateEvent;
 import org.hibernate.event.spi.PreCollectionRecreateEvent;
 import org.hibernate.event.spi.PreCollectionRemoveEvent;
 import org.hibernate.event.spi.PreCollectionUpdateEvent;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
 import org.junit.Before;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.junit4.ExtraAssertions.assertTyping;
 import static org.junit.Assert.assertEquals;
 
@@ -39,6 +41,7 @@ public class MergeCollectionEventTest extends BaseCoreFunctionalTestCase {
 	protected void configure(Configuration configuration) {
 		super.configure( configuration );
 		configuration.setImplicitNamingStrategy( ImplicitNamingStrategyLegacyJpaImpl.INSTANCE );
+		configuration.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
 	}
 
 	private AggregatedCollectionEventListener.IntegratorImpl collectionListenerIntegrator =

hibernate-core/src/test/java/org/hibernate/orm/test/fetchprofiles/CollectionLoadedInTwoPhaseLoadTest.java

@@ -21,12 +21,14 @@ import org.hibernate.annotations.FetchMode;
 import org.hibernate.annotations.FetchProfile;
 import org.hibernate.cfg.Configuration;
 import org.hibernate.cfg.Environment;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
 import org.junit.Assert;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInHibernate;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
@@ -49,6 +51,7 @@ public class CollectionLoadedInTwoPhaseLoadTest extends BaseCoreFunctionalTestCa
 
 	public void configure(Configuration cfg) {
 		cfg.setProperty( Environment.GENERATE_STATISTICS, "true" );
+		cfg.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
 	}
 
 	@Test

hibernate-core/src/test/java/org/hibernate/orm/test/hql/BulkManipulationTest.java

@@ -17,11 +17,14 @@ import java.util.TreeSet;
 import org.hibernate.QueryException;
 import org.hibernate.Session;
 import org.hibernate.Transaction;
+import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+import org.hibernate.cfg.AvailableSettings;
 import org.hibernate.dialect.H2Dialect;
 import org.hibernate.dialect.MySQLDialect;
 import org.hibernate.exception.ConstraintViolationException;
 import org.hibernate.id.BulkInsertionCapableIdentifierGenerator;
 import org.hibernate.id.IdentifierGenerator;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.persister.entity.EntityPersister;
 import org.hibernate.query.Query;
 
@@ -70,6 +73,13 @@ public class BulkManipulationTest extends BaseCoreFunctionalTestCase {
 		return new Class<?>[] { Farm.class, Crop.class };
 	}
 
+
+	@Override
+	protected void prepareBasicRegistryBuilder(StandardServiceRegistryBuilder builer) {
+		super.prepareBasicRegistryBuilder( builer );
+		builer.applySetting( AvailableSettings.DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG );
+	}
+
 	@Test
 	public void testUpdateWithSubquery() {
 		Session s = openSession();

hibernate-core/src/test/java/org/hibernate/orm/test/inheritance/discriminator/TablePerClassInheritancePersistTest.java

@@ -23,19 +23,29 @@ import jakarta.persistence.OneToOne;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.core.Is.is;
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.jupiter.api.Assertions.fail;
 
 /**
  * @author Davide D'Alto
  */
 @TestForIssue(jiraKey = "HHH-12332")
+@ServiceRegistry(
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class
+		)
+)
 @DomainModel(
 		annotatedClasses = {
 				TablePerClassInheritancePersistTest.Family.class,

hibernate-core/src/test/java/org/hibernate/orm/test/insertordering/BaseInsertOrderingTest.java

@@ -8,6 +8,7 @@ import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
 import org.hibernate.cfg.AvailableSettings;
 import org.hibernate.cfg.Environment;
 import org.hibernate.engine.jdbc.connections.spi.ConnectionProvider;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.type.descriptor.java.StringJavaTypeDescriptor;
 import org.hibernate.type.descriptor.jdbc.JdbcType;
 
@@ -55,6 +56,7 @@ abstract class BaseInsertOrderingTest extends BaseSessionFactoryFunctionalTest {
 				.get( AvailableSettings.CONNECTION_PROVIDER );
 		this.connectionProvider.setConnectionProvider( connectionProvider );
 		builer.applySetting( AvailableSettings.CONNECTION_PROVIDER, this.connectionProvider );
+		builer.applySetting( AvailableSettings.DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG );
 	}
 
 

hibernate-core/src/test/java/org/hibernate/orm/test/jpa/cascade/multilevel/MultiLevelCascadeCollectionEmbeddableTest.java

@@ -29,21 +29,30 @@ import jakarta.persistence.Table;
 
 import org.hibernate.testing.FailureExpected;
 import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
 import org.hibernate.testing.orm.junit.Jpa;
 import org.hibernate.testing.orm.junit.EntityManagerFactoryScope;
+import org.hibernate.testing.orm.junit.SettingProvider;
 
 import org.junit.jupiter.api.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 
-@Jpa(annotatedClasses = {
+@Jpa(
+		annotatedClasses = {
 				MultiLevelCascadeCollectionEmbeddableTest.MainEntity.class,
 				MultiLevelCascadeCollectionEmbeddableTest.SubEntity.class,
 				MultiLevelCascadeCollectionEmbeddableTest.AnotherSubSubEntity.class,
 				MultiLevelCascadeCollectionEmbeddableTest.SubSubEntity.class
-})
+		},
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class
+		)
+)
 public class MultiLevelCascadeCollectionEmbeddableTest {
 
 	private boolean initialized = false;

hibernate-core/src/test/java/org/hibernate/orm/test/jpa/cascade/multilevel/MultiLevelCascadeCollectionIdClassTest.java

@@ -28,23 +28,33 @@ import jakarta.persistence.Table;
 
 import org.hibernate.testing.FailureExpected;
 import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
 import org.hibernate.testing.orm.junit.Jpa;
 import org.hibernate.testing.orm.junit.EntityManagerFactoryScope;
+import org.hibernate.testing.orm.junit.Setting;
+import org.hibernate.testing.orm.junit.SettingProvider;
 
 import org.jboss.logging.Logger;
 
 import org.junit.jupiter.api.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 
-@Jpa(annotatedClasses = {
+@Jpa(
+		annotatedClasses = {
 				MultiLevelCascadeCollectionIdClassTest.MainEntity.class,
 				MultiLevelCascadeCollectionIdClassTest.SubEntity.class,
 				MultiLevelCascadeCollectionIdClassTest.AnotherSubSubEntity.class,
 				MultiLevelCascadeCollectionIdClassTest.SubSubEntity.class
-})
+		},
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class
+		)
+)
 public class MultiLevelCascadeCollectionIdClassTest {
 
 	private static final Logger log = Logger.getLogger( MultiLevelCascadeCollectionIdClassTest.class );

hibernate-core/src/test/java/org/hibernate/orm/test/jpa/graphs/queryhint/QueryHintEntityGraphTest.java

@@ -9,6 +9,7 @@ package org.hibernate.orm.test.jpa.graphs.queryhint;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import jakarta.persistence.EntityGraph;
 import jakarta.persistence.EntityManager;
@@ -18,6 +19,7 @@ import jakarta.persistence.Subgraph;
 import org.hibernate.Hibernate;
 import org.hibernate.Session;
 import org.hibernate.jpa.QueryHints;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase;
 import org.hibernate.orm.test.jpa.graphs.Company;
 import org.hibernate.orm.test.jpa.graphs.CompanyFetchProfile;
@@ -32,6 +34,7 @@ import org.hibernate.testing.TestForIssue;
 import org.junit.Before;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -534,4 +537,10 @@ public class QueryHintEntityGraphTest extends BaseEntityManagerFunctionalTestCas
 	protected Class<?>[] getAnnotatedClasses() {
 		return new Class<?>[] { Company.class, CompanyFetchProfile.class, Employee.class, Manager.class, Location.class, Course.class, Student.class };
 	}
+
+	@Override
+	protected void addConfigOptions(Map options) {
+		super.addConfigOptions( options );
+		options.put( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG );
+	}
 }

hibernate-core/src/test/java/org/hibernate/orm/test/manytomany/ManyToManyBidirectionalTest.java

@@ -20,11 +20,15 @@ import org.hibernate.annotations.NaturalId;
 import org.hibernate.dialect.TiDBDialect;
 import org.hibernate.testing.orm.junit.EntityManagerFactoryScope;
 import org.hibernate.testing.orm.junit.FailureExpected;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
 import org.hibernate.testing.orm.junit.Jpa;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.hibernate.testing.orm.junit.SkipForDialect;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
+
 /**
  * @author Vlad Mihalcea
  */
@@ -32,7 +36,11 @@ import org.junit.jupiter.api.Test;
 		annotatedClasses = {
 				ManyToManyBidirectionalTest.Person.class,
 				ManyToManyBidirectionalTest.Address.class,
-		}
+		},
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class
+		)
 )
 public class ManyToManyBidirectionalTest {
 

hibernate-core/src/test/java/org/hibernate/orm/test/mapping/collections/ImplicitListAsBagSemanticsTests.java

@@ -10,12 +10,16 @@ import java.util.Collection;
 import java.util.List;
 
 import org.hibernate.annotations.CollectionClassificationType;
+import org.hibernate.cfg.AvailableSettings;
 import org.hibernate.mapping.Bag;
 import org.hibernate.mapping.Property;
 import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.orm.junit.DomainModel;
 import org.hibernate.testing.orm.junit.DomainModelScope;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.junit.jupiter.api.Test;
 
 import jakarta.persistence.Basic;
@@ -25,17 +29,31 @@ import jakarta.persistence.Id;
 import jakarta.persistence.Table;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 
 /**
+ * Explicitly sets {@link AvailableSettings#DEFAULT_LIST_SEMANTICS} to BAG
+ * and verifies the outcome.
+ *
+ * Basically verifies that the legacy behavior can be achieved via the setting
+ * for users migrating who wish to retain that legacy behavior
+ *
  * @author Steve Ebersole
  */
+@ServiceRegistry(
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class
+		)
+)
 @DomainModel( annotatedClasses = ImplicitListAsBagSemanticsTests.AnEntity.class )
 public class ImplicitListAsBagSemanticsTests {
 	@Test
 	void verifyModel(DomainModelScope scope) {
 		scope.withHierarchy( AnEntity.class, (descriptor) -> {
 			final Property implicitList = descriptor.getProperty( "implicitList" );
-			// because of missing `AvailableSettings.DEFAULT_LIST_SEMANTICS`, this should be BAG (legacy)
+			// this is the purpose of the new AvailableSettings#DEFAULT_LIST_SEMANTICS
+			// setting to allow legacy behavior.
 			assertThat( implicitList.getValue() ).isInstanceOf( Bag.class );
 
 			final Property implicitBag = descriptor.getProperty( "implicitBag" );
@@ -92,4 +110,5 @@ public class ImplicitListAsBagSemanticsTests {
 			this.name = name;
 		}
 	}
+
 }

hibernate-core/src/test/java/org/hibernate/orm/test/mapping/collections/ImplicitListDefaultSemanticsTests.java

@@ -0,0 +1,100 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.orm.test.mapping.collections;
+
+import java.util.Collection;
+import java.util.List;
+
+import org.hibernate.annotations.CollectionClassificationType;
+import org.hibernate.cfg.AvailableSettings;
+import org.hibernate.mapping.Bag;
+import org.hibernate.mapping.Property;
+import org.hibernate.metamodel.CollectionClassification;
+
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.DomainModelScope;
+import org.junit.jupiter.api.Test;
+
+import jakarta.persistence.Basic;
+import jakarta.persistence.ElementCollection;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Table;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Uses the default {@link AvailableSettings#DEFAULT_LIST_SEMANTICS} value of LIST
+ * and verifies the outcome
+ *
+ * @author Steve Ebersole
+ */
+@DomainModel( annotatedClasses = ImplicitListDefaultSemanticsTests.AnEntity.class )
+public class ImplicitListDefaultSemanticsTests {
+	@Test
+	void verifyModel(DomainModelScope scope) {
+		scope.withHierarchy( AnEntity.class, (descriptor) -> {
+			final Property implicitList = descriptor.getProperty( "implicitList" );
+			// this is the change related to AvailableSettings#DEFAULT_LIST_SEMANTICS
+			// previous versions interpreted these as BAG
+			assertThat( implicitList.getValue() ).isInstanceOf( org.hibernate.mapping.List.class );
+
+			final Property implicitBag = descriptor.getProperty( "implicitBag" );
+			assertThat( implicitBag.getValue() ).isInstanceOf( Bag.class );
+
+			final Property explicitBag = descriptor.getProperty( "explicitBag" );
+			assertThat( explicitBag.getValue() ).isInstanceOf( Bag.class );
+
+			final Property explicitList = descriptor.getProperty( "explicitList" );
+			assertThat( explicitList.getValue() ).isInstanceOf( org.hibernate.mapping.List.class );
+		} );
+	}
+
+	@Entity( name = "AnEntity" )
+	@Table( name = "t_entity" )
+	public static class AnEntity {
+	    @Id
+	    private Integer id;
+	    @Basic
+		private String name;
+
+		@ElementCollection
+		private List<String> implicitList;
+
+		@ElementCollection
+		private Collection<String> implicitBag;
+
+		@ElementCollection
+		@CollectionClassificationType( CollectionClassification.BAG )
+		private List<String> explicitBag;
+
+		@ElementCollection
+		@CollectionClassificationType( CollectionClassification.LIST )
+		private List<String> explicitList;
+
+		private AnEntity() {
+			// for use by Hibernate
+		}
+
+		public AnEntity(Integer id, String name) {
+			this.id = id;
+			this.name = name;
+		}
+
+		public Integer getId() {
+			return id;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+	}
+}

hibernate-core/src/test/java/org/hibernate/orm/test/mapping/onetomany/OneToManyBidirectionalTest.java

@@ -589,7 +589,6 @@ public class OneToManyBidirectionalTest {
 	}
 
 	@Test
-	@FailureExpected(jiraKey = "no jira", reason = "order.getLineItems().size() is 4 and not 2 as it should be")
 	public void testItemFetchJoin(SessionFactoryScope scope) {
 		SQLStatementInspector sqlStatementInterceptor = (SQLStatementInspector) scope.getStatementInspector();
 		scope.inTransaction( session -> {

hibernate-core/src/test/java/org/hibernate/orm/test/mapping/onetomany/OneToManyEmptyCollectionTest.java

@@ -17,23 +17,32 @@ import jakarta.persistence.OneToMany;
 import jakarta.persistence.Table;
 
 import org.hibernate.collection.spi.PersistentBag;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
 import org.hibernate.stat.spi.StatisticsImplementor;
 
 import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.junit.jupiter.api.Test;
 
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.CoreMatchers.sameInstance;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.core.IsInstanceOf.instanceOf;
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 /**
  * @author Andrea Boriero
  */
+@ServiceRegistry(
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class )
+)
 @DomainModel(
 		annotatedClasses = {
 				OneToManyEmptyCollectionTest.Order.class,

hibernate-core/src/test/java/org/hibernate/orm/test/namingstrategy/components/ComponentNamingStrategyForJoinColumnTest.java

@@ -14,6 +14,8 @@ import org.hibernate.boot.MetadataSources;
 import org.hibernate.boot.model.naming.ImplicitNamingStrategyComponentPathImpl;
 import org.hibernate.boot.registry.StandardServiceRegistry;
 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+import org.hibernate.cfg.AvailableSettings;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.orm.junit.BaseUnitTest;
@@ -42,7 +44,9 @@ public class ComponentNamingStrategyForJoinColumnTest {
 
 	@Test
 	public void testNamingComponentPath() {
-		final StandardServiceRegistry ssr = new StandardServiceRegistryBuilder().build();
+		final StandardServiceRegistry ssr = new StandardServiceRegistryBuilder()
+				.applySetting( AvailableSettings.DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG )
+				.build();
 
 		try {
 			final MetadataSources ms = new MetadataSources( ssr )

hibernate-core/src/test/java/org/hibernate/orm/test/namingstrategy/components/ComponentNamingStrategyTest.java

@@ -12,11 +12,13 @@ import org.hibernate.boot.model.naming.ImplicitNamingStrategyComponentPathImpl;
 import org.hibernate.boot.model.naming.ImplicitNamingStrategyJpaCompliantImpl;
 import org.hibernate.boot.registry.StandardServiceRegistry;
 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+import org.hibernate.cfg.AvailableSettings;
 import org.hibernate.mapping.Bag;
 import org.hibernate.mapping.Column;
 import org.hibernate.mapping.PersistentClass;
 import org.hibernate.mapping.Property;
 import org.hibernate.mapping.SimpleValue;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.orm.junit.BaseUnitTest;
@@ -34,7 +36,9 @@ public class ComponentNamingStrategyTest {
 
 	@Test
 	public void testDefaultNamingStrategy() {
-		final StandardServiceRegistry ssr = new StandardServiceRegistryBuilder().build();
+		final StandardServiceRegistry ssr = new StandardServiceRegistryBuilder()
+				.applySetting( AvailableSettings.DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG )
+				.build();
 
 		try {
 			final MetadataSources ms = new MetadataSources( ssr );
@@ -60,7 +64,9 @@ public class ComponentNamingStrategyTest {
 	@Test
 	@TestForIssue( jiraKey = "HHH-6005" )
 	public void testComponentSafeNamingStrategy() {
-		final StandardServiceRegistry ssr = new StandardServiceRegistryBuilder().build();
+		final StandardServiceRegistry ssr = new StandardServiceRegistryBuilder()
+				.applySetting( AvailableSettings.DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG )
+				.build();
 
 		try {
 			final MetadataSources ms = new MetadataSources( ssr );

hibernate-core/src/test/java/org/hibernate/orm/test/ondemandload/cache/CacheLazyLoadNoTransTest.java

@@ -30,15 +30,18 @@ import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.persister.collection.CollectionPersister;
 
 import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.ImplicitListAsBagProvider;
 import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
 import org.hibernate.testing.orm.junit.Setting;
+import org.hibernate.testing.orm.junit.SettingProvider;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -46,6 +49,18 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 /**
  * @author Janario Oliveira
  */
+@ServiceRegistry(
+		settings = {
+				@Setting(name = AvailableSettings.ENABLE_LAZY_LOAD_NO_TRANS, value = "true"),
+				@Setting(name = Environment.USE_SECOND_LEVEL_CACHE, value = "true"),
+				@Setting(name = Environment.USE_QUERY_CACHE, value = "true"),
+				@Setting(name = Environment.CACHE_PROVIDER_CONFIG, value = "true"),
+		},
+		settingProviders = @SettingProvider(
+				settingName = DEFAULT_LIST_SEMANTICS,
+				provider = ImplicitListAsBagProvider.class
+		)
+)
 @DomainModel(
 		annotatedClasses = {
 				CacheLazyLoadNoTransTest.Application.class,
@@ -54,14 +69,6 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 		}
 )
 @SessionFactory
-@ServiceRegistry(
-		settings = {
-				@Setting(name = AvailableSettings.ENABLE_LAZY_LOAD_NO_TRANS, value = "true"),
-				@Setting(name = Environment.USE_SECOND_LEVEL_CACHE, value = "true"),
-				@Setting(name = Environment.USE_QUERY_CACHE, value = "true"),
-				@Setting(name = Environment.CACHE_PROVIDER_CONFIG, value = "true"),
-		}
-)
 public class CacheLazyLoadNoTransTest {
 
 	@AfterEach

hibernate-core/src/test/java/org/hibernate/orm/test/unidir/BackrefTest.java

@@ -9,10 +9,13 @@ package org.hibernate.orm.test.unidir;
 import org.hibernate.Hibernate;
 import org.hibernate.Session;
 import org.hibernate.Transaction;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 
@@ -38,6 +41,12 @@ public class BackrefTest extends BaseCoreFunctionalTestCase {
 		return new Class<?>[] { Parent1.class, Child1.class, Child2.class };
 	}
 
+	@Override
+	protected void configure(Configuration configuration) {
+		super.configure( configuration );
+		configuration.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Test
 	public void testBackRef() {
 		Session s = openSession();

hibernate-core/src/test/java/org/hibernate/orm/test/where/annotations/LazyManyToManyNonUniqueIdWhereTest.java

@@ -24,6 +24,8 @@ import org.hibernate.Hibernate;
 import org.hibernate.annotations.Immutable;
 import org.hibernate.annotations.Where;
 import org.hibernate.annotations.WhereJoinTable;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
@@ -31,6 +33,7 @@ import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInHibernate;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -48,6 +51,12 @@ public class LazyManyToManyNonUniqueIdWhereTest extends BaseCoreFunctionalTestCa
 		return new Class[] { Material.class, Building.class, Rating.class, Size.class };
 	}
 
+	@Override
+	protected void configure(Configuration configuration) {
+		super.configure( configuration );
+		configuration.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Before
 	public void setup() {
 		doInHibernate(

hibernate-core/src/test/java/org/hibernate/orm/test/where/annotations/LazyOneToManyNonUniqueIdWhereTest.java

@@ -21,6 +21,8 @@ import jakarta.persistence.Table;
 import org.hibernate.Hibernate;
 import org.hibernate.annotations.Immutable;
 import org.hibernate.annotations.Where;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.metamodel.CollectionClassification;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
@@ -28,6 +30,7 @@ import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 
+import static org.hibernate.cfg.AvailableSettings.DEFAULT_LIST_SEMANTICS;
 import static org.hibernate.testing.transaction.TransactionUtil.doInHibernate;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -45,6 +48,12 @@ public class LazyOneToManyNonUniqueIdWhereTest extends BaseCoreFunctionalTestCas
 		return new Class[] { Material.class, Building.class, Rating.class, Size.class };
 	}
 
+	@Override
+	protected void configure(Configuration configuration) {
+		super.configure( configuration );
+		configuration.setProperty( DEFAULT_LIST_SEMANTICS, CollectionClassification.BAG.name() );
+	}
+
 	@Before
 	public void setup() {
 		doInHibernate(

hibernate-envers/src/test/resources/hibernate.properties

@@ -21,3 +21,6 @@ hibernate.cache.region_prefix hibernate.test
 hibernate.cache.region.factory_class org.hibernate.testing.cache.CachingRegionFactory
 
 hibernate.service.allow_crawling=false
+
+## backwards compatibility wrt bag v. list for "implicit" List mappings
+hibernate.mapping.default_list_semantics=bag

hibernate-testing/src/main/java/org/hibernate/testing/orm/junit/ImplicitListAsBagProvider.java

@@ -0,0 +1,30 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.testing.orm.junit;
+
+import org.hibernate.metamodel.CollectionClassification;
+
+/**
+ * Used as a SettingProvider to enable backwards compatibility regarding
+ * plural {@link java.util.List} mappings when no {@link jakarta.persistence.OrderColumn},
+ * {@link org.hibernate.annotations.ListIndexBase},
+ * {@link org.hibernate.annotations.CollectionId} or other annotations hinting at
+ * the classification to use.
+ *
+ * Historically, Hibernate classified these as BAG.  6.0 changes that to LIST (with an
+ * implied {@link jakarta.persistence.OrderColumn}).
+ *
+ * This setting provider is used to enable the legacy classification
+ *
+ * @author Steve Ebersole
+ */
+public class ImplicitListAsBagProvider implements SettingProvider.Provider<CollectionClassification> {
+	@Override
+	public CollectionClassification getSetting() {
+		return CollectionClassification.BAG;
+	}
+}