c# - 返回始终为空最小起订量

Question

我花了很多时间，看到了不同的答案，但不知道出了什么问题，无论我做什么，我总是得到返回值 null。

我希望返回值是一个对象(模拟对象等)，我可以在其上执行断言操作。如果我对这个概念的理解有误，请告诉我。

[Fact]
public void ProjectTest()
{
    var ProjectServiceMock = new Mock<IProjectService>();
    var ProjectMock = new Mock<IProject>();
    IProject project = ProjectMock.Object;
    ProjectServiceMock.Setup(x => x.CreateProject(new Path("C:"), "S1")).Returns(project);
    var addProjectViewModel = new AddProjectViewModel(ProjectServiceMock.Object);

    IProjectService obj = ProjectServiceMock.Object;
    var result = obj.CreateProject(new Path("C:"), "S1");
}

结果总是null。

Answer 1

您在模拟的设置和调用之间传递了两个单独的实例，因此默认情况下它将返回 null。

你要么使用同一个实例

[Fact]
public void ProjectTest() {
    var ProjectServiceMock = new Mock<IProjectService>();
    var ProjectMock = new Mock<IProject>();
    IProject project = ProjectMock.Object;
    var path = new Path("C:");
    ProjectServiceMock.Setup(x => x.CreateProject(path, "S1")).Returns(project);
    var addProjectViewModel = new AddProjectViewModel(ProjectServiceMock.Object);

    IProjectService obj = ProjectServiceMock.Object;
    var result = obj.CreateProject(path, "S1");
}

或者使用它的参数匹配器并不关心实际的参数实例

[Fact]
public void ProjectTest() {
    var ProjectServiceMock = new Mock<IProjectService>();
    var ProjectMock = new Mock<IProject>();
    IProject project = ProjectMock.Object;
    ProjectServiceMock.Setup(x => x.CreateProject(It.IsAny<Path>(), "S1")).Returns(project);
    var addProjectViewModel = new AddProjectViewModel(ProjectServiceMock.Object);

    IProjectService obj = ProjectServiceMock.Object;
    var result = obj.CreateProject(new Path("C:"), "S1");
}

完成后，可以观察到基本上是在尝试测试模拟框架。提供的示例中没有测试实际代码。

尝试在您的测试中遵循 AAA 方法

[Fact]
public void ProjectTest() {
    //Arrange
    var ProjectServiceMock = new Mock<IProjectService>();
    var ProjectMock = new Mock<IProject>();
    IProject project = ProjectMock.Object;
    ProjectServiceMock
        .Setup(x => x.CreateProject(It.IsAny<Path>(), "S1"))
        .Returns(project);
    //System under test
    var addProjectViewModel = new AddProjectViewModel(ProjectServiceMock.Object);

    //Act
    addProjectViewModel.SomeMethodToTest();
    //...assumption is that `CreateProject(new Path("C:"), "S1")` will get called within
    //...the method under test

    //Assert
    //...now assert expected behavior        
}

引用 Moq Quickstart更好地了解如何使用该模拟框架