如何模拟FHIR Http客户端对CreateAsync调用中的响应

Question

在Hl7.Fhir.Rest.FhirClient库中实现对CreateAsync的调用时，我正在为如何模拟有效的响应而苦苦挣扎。我知道如何使用模拟HttpMessageHandler对象模拟dotnet-httpclient，并注意到有一个消息处理程序参数可以在创建FhirClient时指定。我尝试做的是为创建步骤指定一个消息处理程序，它是一个模拟消息处理程序对象。

这个简化的单元测试试图模拟HttpMessageHandler，并使其从FhirClient的CreateAsync方法调用中返回有效的主体和结果代码。

        [Fact]
        public async Task SubscribeAndReturnSubscriptionIdAsync()
        {
            var mockHttpMessageHandler = MockFhirHttpClientMessageHandler.MockSubscribeMessageResponse(new StringContent("{'id':'abc123','status':'active'}"), HttpStatusCode.Created);
            var subscriptionResource = new Subscription()
            {
                Criteria = "https://server.fire.ly/CareTeam",
                Status = Subscription.SubscriptionStatus.Active,
                Reason = "test",
                Channel = new Subscription.ChannelComponent()
                {
                    Type = Subscription.SubscriptionChannelType.RestHook,
                    Endpoint = "http://localhost:9999/AscomFhirApi/UpdateCareTeam",
                    Payload = "application/fhir+json"
                },
            };
            var serverUri = new Uri("http://server.fire.ly");
            var clientSettings = new FhirClientSettings()
            {
                PreferredFormat = ResourceFormat.Json
            };

            var fhirHttpClient = new Hl7.Fhir.Rest.FhirClient(serverUri, clientSettings, mockHttpMessageHandler.Object);

            var subscription = await fhirHttpClient.CreateAsync<Subscription>(subscriptionResource);

            Assert.NotEmpty(subscription.Id);
        }

下面显示的MockSubscribeMessageResponse方法创建了在上面的测试中传递给FhirClient的HttpMessageHandler。

public static Mock<HttpMessageHandler> MockSubscribeMessageResponse(
            HttpContent content,
            HttpStatusCode code = HttpStatusCode.OK)
        {
            var mockHttpMessageHandler = new Mock<HttpMessageHandler>();
            mockHttpMessageHandler.Protected()
                .Setup<Task<HttpResponseMessage>>("SendAsync", ItExpr.IsAny<HttpRequestMessage>(),
                    ItExpr.IsAny<CancellationToken>())
                .ReturnsAsync(new HttpResponseMessage
                {
                    StatusCode = code,
                    Content = content
                });
            return mockHttpMessageHandler;
        }

我得到的错误是在看起来像HttpResponseMessage或响应体的内容中出现空引用异常。

System.NullReferenceException
Object reference not set to an instance of an object.
   at Hl7.Fhir.Rest.HttpToEntryExtensions.ToEntryResponse(HttpResponseMessage response, Byte[] body)
   at Hl7.Fhir.Rest.HttpClientRequester.ExecuteAsync(EntryRequest interaction)
   at Hl7.Fhir.Rest.BaseFhirClient.executeAsync[TResource](Bundle tx, IEnumerable`1 expect)
   at Tests.Unit.Core.Services.FirelyHttpClientShould.SubscribeAndReturnSubscriptionIdAsync() in C:\src\AscomIASharedAssignFHIRApi5\Tests.Unit.Core\Services\FirelyHttpClientShould.cs:line 60

Answer 1

您可能很久以前就发现了这一点，但是错误的来源很可能是缺少RequestMessage，ToEntryResponse的实现依赖于response.RequestMessage.RequestUri的设置。所以我猜你需要做的是：

var mockHttpMessageHandler = new Mock<HttpMessageHandler>();
mockHttpMessageHandler.Protected()
    .Setup<Task<HttpResponseMessage>>("SendAsync", ItExpr.IsAny<HttpRequestMessage>(), ItExpr.IsAny<CancellationToken>())
    .ReturnsAsync(new HttpResponseMessage
    {
        StatusCode = code,
        RequestMessage = new HttpRequestMessage(HttpMethod.Get, "http://localhost"),
        Content = content
    });
    return mockHttpMessageHandler;