add test showing how to use gen_random_uuid() on postgres

hibernate-core/src/test/java/org/hibernate/orm/test/mapping/generated/sqldefault/PostgresUuidTest.java

@@ -0,0 +1,38 @@
+package org.hibernate.orm.test.mapping.generated.sqldefault;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import org.hibernate.annotations.ColumnDefault;
+import org.hibernate.annotations.Generated;
+import org.hibernate.dialect.PostgreSQLDialect;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.RequiresDialect;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.UUID;
+
+@SessionFactory
+@DomainModel(annotatedClasses = PostgresUuidTest.It.class)
+@RequiresDialect(PostgreSQLDialect.class)
+public class PostgresUuidTest {
+
+	@Test
+	void testit(SessionFactoryScope scope) {
+		scope.inTransaction( s -> s.persist( new It() ) );
+		scope.inTransaction( s -> {
+			UUID uuid = s.createQuery("select uuid from It", UUID.class).getSingleResult();
+			String string = s.createQuery("select str(uuid) from It", String.class).getSingleResult();
+			Assertions.assertEquals( string, uuid.toString() );
+		});
+	}
+
+	@Entity(name="It")
+	public static class It {
+		@Id @Generated
+		@ColumnDefault("gen_random_uuid()")
+		UUID uuid;
+	}
+}