public void ChangeSharePriceDidntExistTest() { // Arrange var shareRepositoryMock = Substitute.For <ISharesRepository>(); var sut = new ShareManager(shareRepositoryMock); int shareID = 135; decimal sharePrice = 1314095; shareRepositoryMock .IsShareExist(Arg.Is <int>(shareID)) .Returns(false); // Act sut.ChangeSharePrice(shareID, sharePrice); // Asserts shareRepositoryMock.DidNotReceive().ChangeSharePrice(Arg.Is <int>(shareID), Arg.Is <decimal>(sharePrice)); }