public void DeleteGrade() { //create the student var newStudent = new Student() { FirstName = "Mikesh", LastName = "Mistry" }; //add the student studentRepository.Add(newStudent); //Find the student var foundStudent = studentRepository.GetAll().ToList(); //create a course var newCourse = new Course() { Name = "Introduction To C# Programming", Description = "Introduction To C# Programming" }; //add the course to the database courseRepository.Add(newCourse); //find the course var foundCourse = courseRepository.GetAll().ToList(); //create a new grade var newGrade = new Grade() { Student = newStudent, Course = newCourse, LetterGrade = "A+" }; //add the grade gradeRepository.Add(newGrade); //find the grade var foundGrade = gradeRepository.Find(grade => grade.Student.StudentId == foundStudent[0].StudentId && grade.Course.CourseId == foundCourse[0].CourseId ).FirstOrDefault(); //test to see if we found the grade Assert.IsNotNull(foundGrade); //delete it gradeRepository.Remove(newGrade); foundGrade = gradeRepository.Find(grade => grade.Student.StudentId == foundStudent[0].StudentId && grade.Course.CourseId == foundCourse[0].CourseId ).FirstOrDefault(); //after deleting found grade should be null Assert.IsNull(foundGrade); }