public void CorrectlyReturnTargetInstance_WhenParamsAreCorrect() { // Arrange var contextMock = new Mock <ITravelGuideContext>(); var imageFactoryMock = new Mock <IGalleryImageFactory>(); var commentFactoryMock = new Mock <IGalleryCommentFactory>(); var likeFactoryMock = new Mock <IGalleryLikeFactory>(); var image = new GalleryImage(); contextMock.Setup(x => x.GalleryImages.Find(It.IsAny <Guid>())).Returns(image); var service = new GalleryImageService(contextMock.Object, imageFactoryMock.Object, likeFactoryMock.Object, commentFactoryMock.Object); // Act var dbImage = service.GetGalleryImageById(Guid.NewGuid()); // Assert Assert.AreSame(image, dbImage); }