如何测试 CacheProvider

Question

我有一个缓存 class 如下：

public class MyCache : ICacheProvider
{ 
    private readonly IMemoryCache _cache; 
    private readonly MemoryCacheOptions _options;
    private readonly ILogger<InMemoryCacheProvider> _logger;  

    public MyCache(IMemoryCache cache, MemoryCacheOptions options, ILogger<InMemoryCacheProvider> logger)
    {
      //Elided
    }

    public virtual void Set<T>(string key, T value, TimeSpan expiration) where T : class
    {  
        _cache.Set(key, value, expiration); 
    } 

    public virtual T Get<T>(string key) where T : class
    { 
        if (_cache.Get(key) is T result)
        { 
            return result; 
        }  
        return default(T);
    } 
    // removed some code for clarity
 }

ICacheProvider 有类似 Set 和 Get 的方法。

我该如何测试这个 class？我需要测试 set 方法是否真的为依赖项设置了一些东西。使用 FakeitEasy，我完成了以下操作：

    [Fact]
    public void SetTest()
    {
        var cache = A.Fake<MyCache>();
        var item = A.Fake<TestClass>();
        cache.Set("item", item);

        A.CallTo(() => cache.Set("item", item)).MustHaveHappened(); 
    }

但这对我来说意义不大。

我感兴趣的是，当我调用 set 方法时，我需要能够检查假缓存中是否真的有一个对象集或其他什么。 Get 和其他方法相同。

能否详细说明一下？

Answer 1

@Nkosi 的评论是正确的。通过模拟被测系统的协作者来使用模拟框架。然后就可以运行被测系统了。像这样：

// mock a collaborator
var fakeCache = A.Fake<IMemoryCache>();

// Create a real system under test, using the fake collaborator.
// Depending on your circumstances, you might want real options and logger,
// or fake options and logger. For this example, it doesn't matter.
var myCacheProvider = new MyCache(fakeCache, optionsFromSomewhere, loggerFromSomewhere);

// exercise the system under test
myCacheProvider.Set("item", item, someExpriation);

// use the fake collaborator to verify that the system under test worked
// As @Nkosi points out, _cache.Set(key, value, expiration)
// from the question is an extension method, so you can't assert on it
// directly. Otherwise you could do
// A.CallTo(() => fakeCache.Set("item", item, expiration)).MustHaveHappened();
// Instead you'll need to assert on CreateEntry, which could be a little trickier

如何测试 CacheProvider

How to test a CacheProvider

.net

c#

unit-testing

moq

fakeiteasy