public void AddCourse(Course course)
        {
            if (course == null)
            {
                throw new ArgumentNullException("The course to add can't be null!");
            }

            this.coursesList.Add(course);
        }
        public void RemoveCourse(Course course)
        {
            if (course == null)
            {
                throw new ArgumentNullException("The course to remove can't be null!");
            }

            this.coursesList.Remove(course);
        }
        public void Test_CourseCantHaveMoreThanThirtyStudents()
        {
            List<Student> students = new List<Student>();
            for (int i = 0; i <= 30; i++)
            {
                students.Add(new Student("Student" + i));
            }

            Course someCourse = new Course(students);
        }
        public void Test_CourseCanHaveStudentsBetweenOneAndThirty()
        {
            List<Student> students = new List<Student>();
            for (int i = 0; i <= 10; i++)
            {
                students.Add(new Student("Student" + i));
            }

            Course someCourse = new Course(students);
        }
        public void Test_NullStudentCantJoinTheCourse()
        {
            List<Student> students = new List<Student>();
            for (int i = 0; i < 10; i++)
            {
                students.Add(new Student("Student" + i));
            }

            Course someCourse = new Course(students);
            someCourse.Join(null);
        }
 public void Test_CourseCantBeCreatedWithEmptyListOfStudents()
 {
     Course someCourse = new Course(new List<Student>());
 }
        public void Test_ThirtyFirstStudentCantJoinTheCourse()
        {
            List<Student> students = new List<Student>();
            for (int i = 0; i < 30; i++)
            {
                students.Add(new Student("Student" + i));
            }

            Course someCourse = new Course(students);
            someCourse.Join(new Student("Pesho"));
        }