c# - 编写可测试的 "import data from database"类

Question

我的任务是从第 3 方供应商的 SQLite 数据表中提取所有行，根据这些记录创建业务对象，并将新的业务对象发送到另一个类。

伪代码:

var databasePath = "%user profile%\application data\some3rdPartyVendor\vendor.sqlite"
var connection = OpenSqliteConnection(databasePath);
var allGizmoRecords = connection.Query(...);
var businessObjects = TransformIntoBizObjs(allGizmoRecords);
someOtherClass.HandleNewBizObjs(businessObjects);

我已经完成了所有工作。

我的问题是:我怎样才能编写这个类以使其可以进行单元测试？

我应该:

• 使用存储库模式模拟数据访问
• 在单元测试中实际提供一个虚拟 SQLite 数据库

或者有什么更好的主意？我正在使用 C#，但这个问题似乎与语言无关。

Answer 1

您可以很容易地注入(inject)一个仅供测试的 Sqlite 数据库，将代码重构为如下所示。但是您如何断言结果？业务对象被传递给 someOtherClass。如果您注入(inject)一个 ISomeOtherClass，该类的操作也需要可见。好像有点疼。

public class KillerApp
{
    private String databasePath;
    private ISomeOtherClass someOtherClass;

    public KillerApp(String databasePath, ISomeOtherClass someOtherClass)
    {
        this.databasePath = databasePath;
        this.someOtherClass = someOtherClass;
    }

    public void DoThatThing()
    {
        var connection = OpenSqliteConnection(databasePath);
        var allGizmoRecords = connection.Query(...);
        var businessObjects = TransformIntoBizObjs(allGizmoRecords);
        someOtherClass.HandleNewBizObjs(businessObjects);
    }
}

[TestClass]
public class When_Doing_That_Thing
{
    private const String DatabasePath = /* test path */;
    private ISomeOtherClass someOtherClass = new SomeOtherClass();
    private KillerApp app;

    [TestInitialize]
    public void TestInitialize()
    {
        app = new KillerApp(DatabasePath, someOtherClass);
    }

    [TestMethod]
    public void Should_convert_all_gizmo_records_to_busn_objects()
    {
        app.DoThatThing();
        Assert.AreEqual(someOtherClass.Results, /* however you're confirming */);
    }
}

使用 IRepository 会从此类中删除一些代码，从而允许您模拟 IRepository 实现，或伪造一个仅用于测试。

public class KillerApp
{
    private IRepository<BusinessObject> repository;
    private ISomeOtherClass someOtherClass;

    public KillerApp(IRepository<BusinessObject> repository, ISomeOtherClass someOtherClass)
    {
        this.repository = repository;
        this.someOtherClass = someOtherClass;
    }

    public void DoThatThing()
    {
        BusinessObject[] entities = repository.FindAll();
        someOtherClass.HandleNewBizObjs(entities);
    }
}

[TestClass]
public class When_Doing_That_Thing
{
    private const String DatabasePath = /* test path */;
    private IRepository<BusinessObject> repository;
    private ISomeOtherClass someOtherClass = new SomeOtherClass();
    private KillerApp app;

    [TestInitialize]
    public void TestInitialize()
    {
        repository = new BusinessObjectRepository(DatabasePath);
        app = new KillerApp(repository, someOtherClass);
    }

    [TestMethod]
    public void Should_convert_all_gizmo_records_to_busn_objects()
    {
        app.DoThatThing();
        Assert.AreEqual(someOtherClass.Results, /* however you're confirming */);
    }
}

但是这样感觉还是挺麻烦的。有两个原因，1) Repository 模式是getting some bad press最近来自 Ayende ，谁对 Repository 略知一二。 2) 你在做什么编写你自己的数据访问!？使用 NHibernate和 ActiveRecord !

[ActiveRecord] /* You define your database schema on the object using attributes */
public BusinessObject
{
    [PrimaryKey]
    public Int32 Id { get; set; }

    [Property]
    public String Data { get; set; }

    /* more properties */
}

public class KillerApp
{
    private ISomeOtherClass someOtherClass;

    public KillerApp(ISomeOtherClass someOtherClass)
    {
        this.someOtherClass = someOtherClass;
    }

    public void DoThatThing()
    {
        BusinessObject[] entities = BusinessObject.FindAll() /* built-in ActiveRecord call! */
        someOtherClass.HandleNewBizObjs(entities);
    }
}

[TestClass]
public class When_Doing_That_Thing : ActiveRecordTest /* setup active record for testing */
{
    private ISomeOtherClass someOtherClass = new SomeOtherClass();
    private KillerApp app;

    [TestInitialize]
    public void TestInitialize()
    {
        app = new KillerApp(someOtherClass);
    }

    [TestMethod]
    public void Should_convert_all_gizmo_records_to_busn_objects()
    {
        app.DoThatThing();
        Assert.AreEqual(someOtherClass.Results, /* however you're confirming */);
    }
}

结果是一个更小的类和一个您可以更容易更改的业务对象和数据层。而且您甚至不必模拟数据库调用，您可以配置和初始化 ActiveRecord 以使用测试数据库(甚至在内存中)。