public async Task DownloadFileNamesTest() { var json = "{ \"Files\":[\"test.pdf\",\"test.txt\"],\"ErrorMessage\":null}"; var response = new HttpResponseMessage { StatusCode = HttpStatusCode.OK, Content = new StringContent(json), }; httpFake .Setup( x => x.GetAsync((It.IsAny <string>()))) .Returns(Task.FromResult <HttpResponseMessage>(response)); service = new DownloadService(httpFake.Object); var fileNames = await service.DownloadFileNames(); Assert.IsTrue(fileNames.Contains("test.pdf")); Assert.IsTrue(fileNames.Contains("test.pdf")); }