public void AddGrade()
{
var grade = 90;
var book = new InMemoryBook("grades", new LetterGrade());
book.AddGrade(grade);
Assert.Equal(90, book.GetLastGrade());
}
public void GetLastGradeDoesNotThrowExceptionIfGradesIsEmpty()
{
var book = new InMemoryBook("grades", new LetterGrade());
var lastGrade = book.GetLastGrade();
Assert.Equal(0, lastGrade);
}