public void GetCourseStudents_CourseFound_ListStudents() { // Arrange var id = Guid.NewGuid(); var students = new List <Student>() { new Student { Id = Guid.NewGuid() } }; CoursesRepository.GetStudents(id).Returns(new ListResult <Student> { Return = students }); // Act var result = _service.GetCourseStudents(id); // Assert Assert.That(result, Is.Not.Null); Assert.That(result.Succeed, Is.True); Assert.That(result.Return, Is.Not.Null.And.Not.Empty); }