Expand docs on VmDatabase

moor/lib/src/ffi/vm_database.dart

@@ -15,7 +15,8 @@ import 'moor_ffi_functions.dart';
 /// implementations.
 typedef DatabaseSetup = void Function(Database database);
 
-/// A moor database that runs on the Dart VM.
+/// A moor database implementation based on `dart:ffi`, running directly in a
+/// Dart VM or an AOT compiled Dart/Flutter application.
 class VmDatabase extends DelegatedDatabase {
   VmDatabase._(DatabaseDelegate delegate, bool logStatements)
       : super(delegate, isSequential: true, logStatements: logStatements);
@@ -51,6 +52,10 @@ class VmDatabase extends DelegatedDatabase {
   /// calling [QueryExecutor.close] on the returned [VmDatabase] will also
   /// [Database.dispose] the [database] passed to this constructor.
   ///
+  /// Using [VmDatabase.opened] may be useful when you want to use the same
+  /// underlying [Database] in multiple moor connections. Moor uses this
+  /// internally when running [integration tests for migrations](https://moor.simonbinder.eu/docs/advanced-features/migrations/#verifying-migrations).
+  ///
   /// {@macro moor_vm_database_factory}
   factory VmDatabase.opened(Database database,
       {bool logStatements = false,

moor_generator/lib/src/services/schema/verifier_impl.dart

@@ -75,7 +75,7 @@ class VerifierImplementation implements SchemaVerifier {
 
   @override
   Future<DatabaseConnection> startAt(int version) {
-    return schemaAt(version).then((schema) => schema.connection);
+    return schemaAt(version).then((schema) => schema.newConnection());
   }
 }