在单个单元测试中多次模拟 httpclient

Question

嗨，我正在尝试模拟 httpclient，显然是强迫它给我我需要的结果。问题是，在我的单元测试中，我必须模拟 httpClient 两次，每次都有不同的响应。

...
...
            var httpReq = new HttpRequestMessage(
            HttpMethod.Get,
            $"{config["MY_TEST_ENDPOINT"]/site1}");

            var myContent = await response.Content.ReadAsStringAsync();
            var myFirstModel = JsonConvert.DeserializeObject<MyFirstModel>(myContent );
...
...

我嘲笑这可能：

...
myMockedHttp
            .Protected()
            .Setup<Task<HttpResponseMessage>>(
                "SendAsync",
                ItExpr.IsAny<HttpRequestMessage>(),
                ItExpr.IsAny<CancellationToken>())
            .ReturnsAsync(new HttpResponseMessage()
            {
                StatusCode = HttpStatusCode.OK,
                Content = new StringContent("[{'id':'0001'," +
                                            "'name':'Jonah'," +
                                            "'street':'Cambridge Street 1234'}]"
                                            )
            })
            .Verifiable();

这会给我一个响应，我可以反序列化和使用它 - 给它一个包含 3 个成员的对象：id、name 和 street。

这对我来说是一个问题 - 我也在同一个单元测试中进行了另一个 httpclient 调用，但我不知道如何模拟它。事情是这样的：

...
...
            var httpReq = new HttpRequestMessage(
            HttpMethod.Get,
            $"{config["MY_TEST_ENDPOINT"]/site2}");

            var httpResponseMsg = await _httpClient.SendAsync(httpReq);

            var myContent = await response.Content.ReadAsStringAsync();
            var myFirstModel = JsonConvert.DeserializeObject<MySecondModel>(myContent );
...
...

最初 - 如果这是唯一的 httpclient 调用，我会像这样嘲笑它：

...
myMockedHttp
            .Protected()
            .Setup<Task<HttpResponseMessage>>(
                "SendAsync",
                ItExpr.IsAny<HttpRequestMessage>(),
                ItExpr.IsAny<CancellationToken>())
            .ReturnsAsync(new HttpResponseMessage()
            {
                StatusCode = HttpStatusCode.OK,
                Content = new StringContent("[{'id':'34'," +
                                            "'insurance':'Etx'," +
                                            "'insider':'daily'," +
                                            "'collectives':'4'}]"
                                            )
            })
            .Verifiable();
...
...

但显然我不能......问题是，我从来没有尝试过这种情况，我有多个 httpclient 调用需要被嘲笑。正如您所看到的，它们以不同的内容响应，因为它们是不同的对象并且需要以这种方式处理。

有谁知道如何解决这个问题？

Answer 1

有时设置模拟可能并不总是最好的方法。因为HttpClient实际上取决于HttpMessageHandler您可以创建一个简单的来处理预期的请求

class TestMessageHandler : HttpMessageHandler {
    private readonly IDictionary<string, HttpResponseMessage> messages;

    public TestMessageHandler(IDictionary<string, HttpResponseMessage> messages) {
        this.messages = messages;
    }

    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) {
        var response = new HttpResponseMessage(HttpStatusCode.NotFound);
        if (messages.ContainsKey(request.RequestUri.ToString()))
            response = messages[request.RequestUri.ToString()] ?? new HttpResponseMessage(HttpStatusCode.NoContent);
        response.RequestMessage = request;
        return Task.FromResult(response);
    }
}

上面的处理程序仅使用传入请求的 URL 在字典中查找响应。如果需要，可以重构它以处理更复杂的请求，但对于简单的请求，这就可以了。

将处理程序传递给为测试创建的客户端

public async Task MyTestMethod() {
    //Arrange
    Dictionary<string, HttpResponseMessage> messages = new Dictionary<string, HttpResponseMessage>();
    messages.Add("https://somesite1.com/ping", new HttpResponseMessage() {
        StatusCode = HttpStatusCode.OK,
        Content = new StringContent("[{'id':'0001'," +
                                    "'name':'Jonah'," +
                                    "'street':'Cambridge Street 1234'}]"
                                    )
    });
    messages.Add("https://somesite2.com/ping", new HttpResponseMessage() {
        StatusCode = HttpStatusCode.OK,
        Content = new StringContent("[{'id':'34'," +
                                    "'insurance':'Etx'," +
                                    "'insider':'daily'," +
                                    "'collectives':'4'}]"
                                    )
    });

    var client = new HttpClient(new TestMessageHandler(messages));

    //...inject client as needed

现在，在验证被测对象的预期行为时，可以根据需要调用具有自定义处理程序的客户端。