嘲弄HttpResponse WriteAsync

Question

我试图在模拟的WriteAsync上调用一个模拟HttpResponse，但我找不出要使用的语法。

var responseMock = new Mock<HttpResponse>();
responseMock.Setup(x => x.WriteAsync(It.IsAny<string>(), It.IsAny<CancellationToken>()));

ctx.Setup(x => x.Response).Returns(responseMock.Object);

带有以下错误的测试炸弹：

System.NotSupportedException :扩展方法上的无效设置:X => x.WriteAsync(It.IsAny()，It.IsAny())

最终，我想验证正确的字符串已经写入响应。

如何正确设置这个？

Answer 1

Moq不能Setup扩展方法。如果您知道扩展方法访问什么，那么有些情况下可以通过扩展方法模拟安全路径。

WriteAsync(HttpResponse，String，CancellationToken)

将给定的文本写入响应体。将使用UTF-8编码。

通过以下重载直接访问HttpResponse.Body.WriteAsync，其中Body是Stream

/// <summary>
/// Writes the given text to the response body using the given encoding.
/// </summary>
/// <param name="response">The <see cref="HttpResponse"/>.</param>
/// <param name="text">The text to write to the response.</param>
/// <param name="encoding">The encoding to use.</param>
/// <param name="cancellationToken">Notifies when request operations should be cancelled.</param>
/// <returns>A task that represents the completion of the write operation.</returns>
public static Task WriteAsync(this HttpResponse response, string text, Encoding encoding, CancellationToken cancellationToken = default(CancellationToken))
{
    if (response == null)
    {
        throw new ArgumentNullException(nameof(response));
    }

    if (text == null)
    {
        throw new ArgumentNullException(nameof(text));
    }

    if (encoding == null)
    {
        throw new ArgumentNullException(nameof(encoding));
    }

    byte[] data = encoding.GetBytes(text);
    return response.Body.WriteAsync(data, 0, data.Length, cancellationToken);
}

这意味着您需要模拟response.Body.WriteAsync。

//Arrange
var expected = "Hello World";
string actual = null;
var responseMock = new Mock<HttpResponse>();
responseMock
    .Setup(_ => _.Body.WriteAsync(It.IsAny<byte[]>(),It.IsAny<int>(), It.IsAny<int>(), It.IsAny<CancellationToken>()))
    .Callback((byte[] data, int offset, int length, CancellationToken token)=> {
        if(length > 0)
            actual = Encoding.UTF8.GetString(data);
    })
    .ReturnsAsync();

//...code removed for brevity

//...
Assert.AreEqual(expected, actual);

回调用于捕获传递给模拟成员的参数。它的值存储在一个变量中，以便在稍后的测试中声明。

Answer 2

为了完整起见，这里有一个在.NET Core3.1中工作的解决方案：

const string expectedResponseText = "I see your schwartz is as big as mine!";

DefaultHttpContext httpContext = new DefaultHttpContext();
httpContext.Response.Body = new MemoryStream();

// Whatever your test needs to do

httpContext.Response.Body.Position = 0;
using (StreamReader streamReader = new StreamReader(httpContext.Response.Body))
{
    string actualResponseText = await streamReader.ReadToEndAsync();
    Assert.Equal(expectedResponseText, actualResponseText);
}