模拟 HttpResponse WriteAsync

Question

我正在尝试WriteAsync在模拟上调用模拟HttpResponse，但我无法弄清楚要使用的语法。

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：扩展方法的设置无效：x => x.WriteAsync(It.IsAny(), It.IsAny())

最终，我想验证是否已将正确的字符串写入响应。

如何正确设置？

Answer 1

Moq 不能Setup扩展方法。如果您知道扩展方法访问什么，那么在某些情况下，您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正文。将使用 UTF-8 编码。

通过以下重载直接访问HttpResponse.Body.WriteAsyncwhere Bodyis aStream

/// <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);
}

这意味着你需要模拟 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，以便稍后在测试中进行断言。

Answer 2

为了完整性，这里有一个似乎适用于 .NET Core 3.1 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);
}