c# - 如何在代码中找到单元测试必须覆盖的地方

Question

我知道在实际编写代码后编写测试不太好。我是单元测试的新手，觉得单元测试可以带来很多好处，所以我痴迷于尽可能多地覆盖的想法。

例如，让我们有这样的代码:

public class ProjectsPresenter : IProjectsViewObserver
{
    private readonly IProjectsView _view;
    private readonly IProjectsRepository _repository;

    public ProjectsPresenter(IProjectsRepository repository, IProjectsView view)
    {
        _view = view;
        _repository = repository;
        Start();
    }

    public void Start()
    {
        _view.projects = _repository.FetchAll();
        _view.AttachPresenter(this);
    }

}

所以看看上面的代码，你能回答我通常应该在上面的那段代码上写什么测试吗？

我正在对构造函数进行编写测试，以确保调用了存储库的 FetchAll 并调用了 View 站点上的 AttachPresenter。

---

后期编辑

这是我的 View 界面:

public interface IProjectsView
{
    List<Project> projects { set; }
    Project project { set; }

    void AttachPresenter(IProjectsViewObserver projectsPresenter);
}

这是一个 View :

public partial class ProjectsForm : DockContent, IProjectsView
{
    private IProjectsViewObserver _presenter;
    public ProjectsForm()
    {
        InitializeComponent();
    }

    public Project project
    {
        set
        {
            listBoxProjects.SelectedItem = value;
        }
    }

    public List<Project> projects
    {
        set
        {
            listBoxProjects.Items.Clear();   
            if ((value != null) && (value.Count() > 0))
                listBoxProjects.Items.AddRange(value.ToArray());
        }
    }

    public void AttachPresenter(IProjectsViewObserver projectsPresenter)
    {
        if (projectsPresenter == null)
            throw new ArgumentNullException("projectsPresenter");

        _presenter = projectsPresenter;
    }

    private void listBoxProjects_SelectedValueChanged(object sender, EventArgs e)
    {
        if (_presenter != null)
            _presenter.SelectedProjectChanged((Project)listBoxProjects.SelectedItem);
    }
}

---

发布编辑#2

这就是我测试与存储库交互的方式。一切都好吗？

    [Test]
    public void ProjectsPresenter_RegularProjectsProcessing_ViewProjectsAreSetCorrectly()
    {
        // Arrange
        MockRepository mocks = new MockRepository();
        var view = mocks.StrictMock<IProjectsView>();
        var repository = mocks.StrictMock<IProjectsRepository>();
        List<Project> projList = new List<Project> {
            new Project { ID = 1, Name = "test1", CreateTimestamp = DateTime.Now },
            new Project { ID = 2, Name = "test2", CreateTimestamp = DateTime.Now }
        };
        Expect.Call(repository.FetchAll()).Return(projList);
        Expect.Call(view.projects = projList);
        Expect.Call(delegate { view.AttachPresenter(null); }).IgnoreArguments();
        mocks.ReplayAll();
        // Act
        ProjectsPresenter presenter = new ProjectsPresenter(repository, view);
        // Assert
        mocks.VerifyAll();            
    }

Answer 1

I know it's not so good to write tests after you actually wrote code

总比不写测试要好。

您的方法适用于两个外部组件，并且应该验证该交互(除了提到的参数验证之外)。检查 FetchAll 是否被调用没有给你任何值(value)(或者检查它返回东西 - 这属于 ProjectsRepository 测试自己) - 您要检查 View 的项目是否已设置(这将间接检查是否调用了 FetchAll)。您需要的测试是:

• 验证 View 项目是否设置为预期值
• 验证演示者已连接
• 验证输入参数

编辑:您将如何测试第一个案例的示例(项目已设置)

// "RegularProcessing" in test name feels a bit forced;
// in such cases, you can simply skip 'conditions' part of test name
public void ProjectsPresenter_SetsViewProjectsCorrectly()
{
    var view = MockRepository.GenerateMock<IProjectView>();
    var repository = MockRepository.GenerateMock<IProjectsRepository>();
    // Don't even need content;
    // reference comparison will be enough
    List<Project> projects = new List<Project>();
    // We use repository in stub mode;
    // it will simply provide data and that's all
    repository.Stub(r => r.FetchAll()).Return(projects);
    view.Expect(v => v.projects = projects);

    ProjectsPresenter presenter = new ProjectsPresenter(repository, view);

    view.VerifyAllExpecations();
}

在第二种情况下，您将期望其 AttachPresenter 被有效对象调用:

public void ProjectsPresenter_AttachesPresenterToView()
{
    // Arrange
    var view = MockRepository.GenerateMock<IProjectView>();
    view.Expect(v => v.AttachPresenter(Arg<IProjectsViewObserver>.Is.Anything));
    var repository = MockRepository.GenerateMock<IProjectsRepository>();

    // Act
    var presenter = new ProjectsPresenter(repository, view);

    // Assert
    view.VerifyAllExpectations();
}