A good example of Fluent Mocking (see http://rodrigodumont.com/2013/09/26/fluent-mocking-for-unit-tests/)

HttpMessageHandlerExtensions.cs

public static class HttpMessageHandlerExtensions
{
    public static HttpMessageHandler ThatRespondsWithAnEmptyContent(this HttpMessageHandler handler)
    {
        var mock = Mock.Get(handler);
        var responseWithAnEmptyContent = new HttpResponseMessage {Content = new StringContent(string.Empty)};

        mock.Protected()
            .Setup<Task<HttpResponseMessage>>("SendAsync", new object[] 
                {
                    ItExpr.IsAny<HttpRequestMessage>(),
                    ItExpr.IsAny<CancellationToken>()
                })
            .Returns(Task.FromResult(responseWithAnEmptyContent));

        return handler;
    }
}