public void FindById_ReturnsDay_FindByDoctorId([NotNull] IDay day) { // Arrange var repository = Substitute.For <IDaysRepository>(); repository.FindByDoctorId(1).Returns(CreateList); InformationFinder sut = CreateSut(repository); // Act IEnumerable <IDayForResponse> actual = sut.FindByDoctorId(1); // Assert Assert.Equal(2, actual.Count()); }