使用Rhino Mocks进行单元测试INotifyPropertyChanged

Question

我有一个实现INotifyPropertyChanged的类，我需要测试此接口是否正确实现。我想使用Rhino Mock对象执行此操作。

class MyClass : INotifyPropertyChanged
{
    public int X
    {
        get => ...;
        set => ... // should check if value changes and raise event PropertyChanged
    }
}

我要测试的是，当X更改值时，该事件PropertyChanged会使用适当的参数精确地调用一次。

MyClass testObject = new MyClass();

// the mock:
PropertyChangedEventHandler a = MockRepository.GenerateMock<PropertyChangedEventHandler>();
testObject.PropertyChanged += a;

// expect that the mock will be called exactly once, with the proper parameters
a.Expect( (x) => ???)
 .Repeat()
 .Once();

// change X, and verify that the event handler has been called exactly once
testObject.X = testObject.X + 1;

a.VerifyAllExpectations(); ???

我认为我走在正确的道路上，但我无法正常工作。

Answer 1

有时，如果没有使用实物的连锁效应，确实不需要使用模拟。

下面的简单示例创建委托的实例并验证预期的行为

我要测试的是，当X更改值时，该事件PropertyChanged将使用适当的参数精确地调用一次。

[TestClass]
public class MyClassTests {
    [TestMethod]
    public void Should_Call_PropertyChanged_Once() {
        //Arrange            
        //Store calls
        IDictionary<string, int> properties = new Dictionary<string, int>();
        PropertyChangedEventHandler handler = new PropertyChangedEventHandler((s, e) => {
            if (!properties.ContainsKey(e.PropertyName))
                properties.Add(e.PropertyName, 0);

            properties[e.PropertyName]++;
        });

        MyClass testObject = new MyClass();
        testObject.PropertyChanged += handler;

        //Act
        testObject.X = testObject.X + 1;

        //Assert - using FluentAssertions
        string expectedPropertyName = nameof(MyClass.X);
        int expectedCount = 1;
        properties.Should().ContainKey(expectedPropertyName);
        properties[expectedPropertyName].Should().Be(expectedCount);
    }

    class MyClass : INotifyPropertyChanged {
        public event PropertyChangedEventHandler PropertyChanged = delegate { };

        void raisePropertyChanged([CallerMemberName]string propertyName = null) {
            PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        int x;
        public int X {
            get => x;
            set {
                if (value != x) {
                    x = value;
                    raisePropertyChanged();
                }
            }
        }
    }
}