如何模拟返回Task< IEnumerable< T>>的方法与Task< List< T>>吗? [英] How to mock a method returning Task<IEnumerable<T>> with Task<List<T>>?

问题描述

我正在尝试在模拟接口方法的地方设置单元测试初始化​​程序(在Moq中):

public interface IRepository
{
    Task<IEnumerable<myCustomObject>> GetSomethingAsync(string someStringParam);
}

...

[TestInitialize]
public void Initialize()
{
    var repoMock = new Mock<IRepository>();

    var objectsList = new List<myCustomObject>() {
        new myCustomObject("Something"), 
        new myCustomObject("Otherthing")
    }

    repoMock.Setup<Task<IEnumerable<myCustomObject>>>(
        rep => rep.GetSomethingAsync("ThisParam")
    ).Returns(Task.FromResult(objectsList)); //error here
}

我遇到的问题是我不知道如何获取返回我的objectsList的方法.实际上，这当然可以正常工作，因为List实现了IEnumerable，但是当以Moq封装在Task中时，它似乎不起作用.我得到的错误是在Returns()方法上:

Argument 1: cannot convert from 'System.Threading.Tasks.Task<
  System.Collections.Generic.List<myCustomObject>>'
to 'System.Threading.Tasks.Task<
  System.Collections.Generic.IEnumerable<myCustomObject>>'

作为一种解决方法，我可以创建另一个方法，该方法仅创建List<myObj>并将其返回为IEnumerable<myObj>，但是我觉得必须有另一种方法来处理此问题. /p>

那么，如何在不创建帮助器方法的情况下执行此操作?

解决方案

您需要在Task.FromResult上指定<IEnumerable<myCustomObject>>，如下所示:

[TestInitialize]
public void Initialize()
{
    var repoMock = new Mock<IRepository>();

    var objectsList = new List<myCustomObject>() {
        new myCustomObject("Something"), 
        new myCustomObject("Otherthing")
    }

    repoMock.Setup<Task<IEnumerable<myCustomObject>>>(
        rep => rep.GetSomethingAsync("ThisParam")
    ).Returns(Task.FromResult<IEnumerable<myCustomObject>>(objectsList));
}

或者，您可以在从List<myCustomObject>分配objectList之前将其声明为<IEnumerable<myCustomObject>>.不需要先前的建议.

I'm attempting to set up a unit test initializer (in Moq) where an interface method is being mocked:

public interface IRepository
{
    Task<IEnumerable<myCustomObject>> GetSomethingAsync(string someStringParam);
}

...

[TestInitialize]
public void Initialize()
{
    var repoMock = new Mock<IRepository>();

    var objectsList = new List<myCustomObject>() {
        new myCustomObject("Something"), 
        new myCustomObject("Otherthing")
    }

    repoMock.Setup<Task<IEnumerable<myCustomObject>>>(
        rep => rep.GetSomethingAsync("ThisParam")
    ).Returns(Task.FromResult(objectsList)); //error here
}

The issue I'm having is I can't figure out how to get the method to return my objectsList. In practice this of course works fine because List implements IEnumerable, but it doesn't seem to work when wrapped in a Task, in Moq. The error I get is on the Returns() method:

Argument 1: cannot convert from 'System.Threading.Tasks.Task<
  System.Collections.Generic.List<myCustomObject>>'
to 'System.Threading.Tasks.Task<
  System.Collections.Generic.IEnumerable<myCustomObject>>'

As a workaround I can create another method that simply creates the List<myObj> and returns it as IEnumerable<myObj>, but I feel like there must be another way to handle this that is cleaner.

So, how would I do this without having to create the helper method?

解决方案

You need to specify the <IEnumerable<myCustomObject>> on the Task.FromResult, like this:

[TestInitialize]
public void Initialize()
{
    var repoMock = new Mock<IRepository>();

    var objectsList = new List<myCustomObject>() {
        new myCustomObject("Something"), 
        new myCustomObject("Otherthing")
    }

    repoMock.Setup<Task<IEnumerable<myCustomObject>>>(
        rep => rep.GetSomethingAsync("ThisParam")
    ).Returns(Task.FromResult<IEnumerable<myCustomObject>>(objectsList));
}

Alternatively you could declare your objectList as <IEnumerable<myCustomObject>> before assigning it from the List<myCustomObject>. Making the previous suggestion not required.

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