public void InitialRequestIsNullWhenPagingAfterThrows() { // given Func <FakePageRequest, Task <PagedResponse <string> > > pager = _ => Task.FromResult(new PagedResponse <string>()); var subject = new Pager <FakePageRequest, string>(pager); // when AsyncTestDelegate test = () => subject.AndGetAllAfterAsync(); // then var ex = Assert.ThrowsAsync <InvalidOperationException>(test); Assert.That(ex.Message, Is.Not.Null.And.Not.Empty); }