public void AddStudentToCourseReturnsStudenttCourse()
{
//Arrange
repository.Setup(r => r.AddToCourse(It.IsAny <long>(), It.IsAny <long>())).ReturnsAsync(new StudentCourse());
repository.Setup(r => r.Exists(It.IsAny <object[]>())).ReturnsAsync(true);
//Act
var result = (controller.AddStudentToCourse(1, 1).Result as OkObjectResult)?.Value;
//Assert
Assert.IsInstanceOfType(result, typeof(StudentCourse));
}