[Test]
        public void JoinToCourse_ShouldAddStudentToCourseSuccessfully_WitoutThrowException()
        {
            //Arrange
            Mock<IStudent> mockedStudent = new Mock<IStudent>();
            Mock<ICourse> mockedCourse = new Mock<ICourse>();

            //Act
            mockedCourse.Object.JoinToCourse(mockedStudent.Object);

            //Assert
            mockedCourse.Verify(x => x.JoinToCourse(It.IsAny<IStudent>()), Times.Exactly(1));
        }