public void HttpError()
{
// Arrange
A.CallTo(_mockMessageHandler)
.Where(x => x.Method.Name == "SendAsync")
.WithReturnType <Task <HttpResponseMessage> >()
.Returns(Task.FromResult(new HttpResponseMessage
{
StatusCode = HttpStatusCode.InternalServerError,
Content = new StringContent("abcd")
}));
// Act
var result = _systemUnderTest.DoSomething();
// Assert
// Assert.AreEqual(...);
}