public void Test1()
{
//arrange
GradeBook gradeBook = new GradeBook();
gradeBook.Addgrade(57.3);
gradeBook.Addgrade(79.4);
gradeBook.Addgrade(98.5);
gradeBook.Addgrade(55.3);
//act
var stat = gradeBook.GetStatistics();
//assert
Assert.Equal(55.3, stat.Lowgrade);
}