/**
     * Test calculation of the average student grade.
     */
    void test_calc_avg() {
        //Using the included grades.txt file, check the averages of a few students.
        //One with less than max student grades, one with max.
        Students test;
        std::string testFile = "grades.txt";
        test.read_file(testFile);
        double grade;
        grade = test.calc_avg(test.getStudentGrades(0), test.getMaxGradeCount());
        TS_ASSERT_EQUALS(grade, 49);

        grade = test.calc_avg(test.getStudentGrades(97), test.getMaxGradeCount());
        //Check to 4 decimal places.
        TS_ASSERT_DELTA(grade, 86.4545, .00009);

        grade = test.calc_avg(test.getStudentGrades(99), test.getMaxGradeCount());
        //Check to 4 decimal places.
        TS_ASSERT_DELTA(grade, 71.3636, .00009);
    }