public void PostUploadImage_ShouldUpload() { var expectedLink = "link"; var file = Substitute.For <IFormFile>(); var fileStreamMock = new MemoryStream(); file.OpenReadStream().Returns(fileStreamMock); _imgurGateway.UploadImage(fileStreamMock).Returns(expectedLink); var results = _controller.PostUploadImage(file).Result; Assert.AreEqual(expectedLink, results); }