public void GetShareTypeDidntExistTest() { // Arrange var shareRepositoryMock = Substitute.For <ISharesRepository>(); var sut = new SharesService(shareRepositoryMock); int shareID = 12; shareRepositoryMock .DoesShareExists(Arg.Is <int>(shareID)) .Returns(false); // Act sut.GetShareType(shareID); // Asserts shareRepositoryMock.DidNotReceive().GetShareType(Arg.Is <int>(shareID)); }