c# - 复制内存中的 SQLite 数据库，使单元测试更快

Question

在 C#/nHibernate-projects 中，我使用 SQLite 对我的代码进行单元测试，大致使用此处描述的方法:http://ayende.com/blog/3983/nhibernate-unit-testing .

但是，我发现构建和配置内存数据库通常需要大约 150 毫秒。我有很多单元测试，所以这很快就会加起来。

我想一次构建和配置数据库，将其存储在静态变量中，并在每次单元测试需要数据库时复制它。

如何备份内存数据库？

我首先尝试创建一个命名的内存数据库。根据https://www.sqlite.org/inmemorydb.html这个有可能。我曾经有:

    private const string ConnectionString = "Data Source=:memory:;Version=3;";

我试过的连接字符串是:

    private const string ConnectionString = "FullUri=file:memorydb.db?mode=memory&cache=shared";
    private const string ConnectionString2 = "FullUri=file:memorydb2.db?mode=memory&cache=shared";

所以现在我只需要找出如何快速将内容从一个复制到另一个？我快完成了:我可以创建两个内存数据库，并调用“BackupDatabase”来复制数据库。

然而，单元测试的行为就像“实例”数据库没有表，即使是“原型(prototype)”数据库也是如此。

        private static ISessionFactory _prototypeSessionFactory;
        private const string InstanceConnectionString = "FullUri=file:memorydb.db?mode=memory&cache=shared";

        private const string PrototypeConnectionString = "FullUri=file:memorydb2.db?mode=memory&cache=shared";
        private SQLiteConnection _instanceConnection;
        private ISessionFactory _instanceSessionFactory;

        public DatabaseScope(Assembly assembly)
        {
            var prototyeConfiguration = SQLiteConfiguration.Standard.ConnectionString(PrototypeConnectionString);
            var cfg = Fluently
                .Configure()
                .Database(prototyeConfiguration)
                .Mappings(m => m.HbmMappings.AddFromAssembly(assembly));
            cfg.ExposeConfiguration(BuildSchema);
            _prototypeSessionFactory = cfg.BuildSessionFactory();

            var instanceConfiguration = SQLiteConfiguration.Standard.ConnectionString(InstanceConnectionString);
            _instanceSessionFactory = Fluently
                .Configure()
                .Database(instanceConfiguration)
                .BuildSessionFactory();

            CopyDatabase();
        }

        private void CopyDatabase()
        {
            var cnnIn = new SQLiteConnection(PrototypeConnectionString);
            var cnnOut = new SQLiteConnection(InstanceConnectionString);
            cnnIn.Open();
            cnnOut.Open();
            cnnIn.BackupDatabase(cnnOut, "main", "main", -1, null, -1);
            cnnIn.Close();
            cnnOut.Close();
        }

Answer 1

我最终得到了这段工作代码。我的单元测试时间从十多分钟缩短到不到两分钟。(为了便于阅读，代码略有简化)

using System;
using System.Data;
using System.Data.SQLite;
using System.IO;
using System.Reflection;
using FluentNHibernate.Cfg;
using FluentNHibernate.Cfg.Db;
using NHibernate;
using NHibernate.Mapping;
using NHibernate.Tool.hbm2ddl;

namespace TestHelper.DbHelper.SqLite
{
    public class DatabaseScope : IDisposable
    {
        private static Assembly _prototypeAssembly;
        private const string PrototypeConnectionString = "FullUri=file:prototype.db?mode=memory&cache=shared";
        private static ISessionFactory _prototypeSessionFactory;
        private static SQLiteConnection _prototypeConnection;

        private const string InstanceConnectionString = "FullUri=file:instance.db?mode=memory&cache=shared";
        private ISessionFactory _instanceSessionFactory;
        private SQLiteConnection _instanceConnection;

        public DatabaseScope(Assembly assembly)
        {
            InitDatabasePrototype(assembly);
            InitDatabaseInstance();
        }

        private void InitDatabasePrototype(Assembly assembly)
        {
            if (_prototypeAssembly == assembly) return;

            if (_prototypeConnection != null)
            {
                _prototypeConnection.Close();
                _prototypeConnection.Dispose();
                _prototypeSessionFactory.Dispose();
            }

            _prototypeAssembly = assembly;

            _prototypeConnection = new SQLiteConnection(PrototypeConnectionString);
            _prototypeConnection.Open();

            _prototypeSessionFactory = Fluently
                .Configure()
                .Database(SQLiteConfiguration.Standard.ConnectionString(PrototypeConnectionString))
                .Mappings(m => m.HbmMappings.AddFromAssembly(assembly))
                .ExposeConfiguration(cfg => new SchemaExport(cfg).Execute(false, true, false, _prototypeConnection, null))
                .BuildSessionFactory();
        }

        private void InitDatabaseInstance()
        {
            _instanceSessionFactory = Fluently
                .Configure()
                .Database(SQLiteConfiguration.Standard.ConnectionString(InstanceConnectionString))
                .Mappings(m => m.HbmMappings.AddFromAssembly(_prototypeAssembly))
                .BuildSessionFactory();

            _instanceConnection = new SQLiteConnection(InstanceConnectionString);
            _instanceConnection.Open();

            _prototypeConnection.BackupDatabase(_instanceConnection, "main", "main", -1, null, -1);
        }

        public ISession OpenSession()
        {
            return _instanceSessionFactory.OpenSession(_instanceConnection);
        }

        public void Dispose()
        {
            _instanceConnection.Close();
            _instanceConnection.Dispose();
            _instanceSessionFactory.Dispose();
        }
    }
}