C# 模拟具体类。如何？

Question

我想模拟一个具体的类，具体来说是 SortedDictionary。

上下文:

我有一个如下定义的 LocationMapper 类:

public class LocationMapper
{
  private SortedDictionary<string, Location>() locationMap;
  public LocationMapper()
  {
    this.locationMap = new SortedDictionary<string, Location>();
  }

  public LocationMapper(SortedDictionary<string, Location> locations)
  {
    this.locationMap = locations;
  }

  public Location AddLocation(Location location)
  {
    if(! locationMap.ContainsKey(location.Name))
    {
      locationMap.Add(location.Name, location)
    }
    return locationMap[location.Name];
  }  
}

要对 AddLocation() 进行单元测试，我需要模拟具体类 SortedDictionary<>。不幸的是，NSubstitute 不允许这样做。

The unit test that I had envisioned to write is below
[Test]
public void AddLocation_ShouldNotAddLocationAgainWhenAlreadyPresent()
{
  var mockLocationMap = ;//TODO
  //Stub mockLocationMap.ContainsKey(Any<String>) to return "true"
  locationMapper = new LocationMapper(mockLocationMap);
  locationMapper.AddLocation(new Location("a"));
  //Verify that mockLocationMap.Add(..) is not called
}

您将如何在 DotNet 中以这种方式编写单元测试？或者您不为已知的限制走这条路？

非常感谢您的帮助。

Answer 1

另一种方法是使用允许您模拟具体类的单元测试工具，例如我正在使用 Typemock Isolator 并且能够创建您想要进行的测试:

[TestMethod]
public void TestMethod1()
{
    var fakeLocationMap = Isolate.Fake.Instance<SortedDictionary<string, Location>>();

    Isolate.WhenCalled(() => fakeLocationMap.ContainsKey(string.Empty)).WillReturn(true);

    var instance = new LocationMapper(fakeLocationMap);
    var res = instance.AddLocation(new Location("a"));

    Isolate.Verify.WasNotCalled(() => fakeLocationMap.Add(string.Empty, null));
}