public void Enrol_CourseIdIsEmpty_Fail()
        {
            // Arrange
            var courseId = Guid.Empty;
            var student  = StudentsRepository.FoundEntity();

            // Act
            var result = _service.Enrol(student.Id, courseId);

            // Assert
            Assert.That(result, Is.Not.Null);
            Assert.That(result.Succeed, Is.False);
        }