public void BookCalculatesStats()
{
//arrange
var book = new InMemoryBook("");
book.AddGrade(13.3);
book.AddGrade(22.3);
book.AddGrade(23.3);
//act
var result = book.GetStatistic();
//assert
Assert.Equal(23.3, result.High, 1);
Assert.Equal(13.3, result.Low, 1);
Assert.Equal(19.6, result.Average, 1);
Assert.Equal('C', result.Letter);
}
