How to create JUnit test for the following class:

public class GradeBook { private String courseName; // name of course this grade book represents private int grades[][]; // two-dimensional array of student grades public GradeBook( String name, int gradesArray[][] ) { courseName = name; // initialize courseName grades = gradesArray; // store grades } // end two-argument GradeBook constructor public void setCourseName( String name ) { courseName = name; // store the course name } // end method setCourseName public String getCourseName() { return courseName; } // end method getCourseName public void displayMessage() { System.out.printf( "Welcome to the grade book for %s! ", getCourseName() ); } // end method displayMessage public void processGrades() { outputGrades(); System.out.printf( " %s %d %s %d ", "Lowest grade in the grade book is", getMinimum(), "Highest grade in the grade book is", getMaximum() ); outputBarChart(); } // end method processGrades public int getMinimum() { int lowGrade = grades[ 0 ][ 0 ]; for ( int studentGrades[] : grades ) { for ( int grade : studentGrades ) { if ( grade < lowGrade ) lowGrade = grade; } // end inner for } // end outer for return lowGrade; } // end method getMinimum public int getMaximum() { int highGrade = grades[ 0 ][ 0 ]; for ( int studentGrades[] : grades ) { for ( int grade : studentGrades ) { if ( grade > highGrade ) highGrade = grade; } // end inner for } // end outer for return highGrade; } // end method getMaximum public double getAverage( int setOfGrades[] ) { int total = 0; // initialize total for ( int grade : setOfGrades ) total += grade; return (double) total / setOfGrades.length; } // end method getAverage public void outputBarChart() { System.out.println( "Overall grade distribution:" ); int frequency[] = new int[ 11 ]; for ( int studentGrades[] : grades ) { for ( int grade : studentGrades ) ++frequency[ grade / 10 ]; } // end outer for for ( int count = 0; count < frequency.length; count++ ) { if ( count == 10 ) System.out.printf( "%5d: ", 100 ); else System.out.printf( "%02d-%02d: ", count * 10, count * 10 + 9 ); for ( int stars = 0; stars < frequency[ count ]; stars++ ) System.out.print( "*" ); System.out.println(); // start a new line of output } // end outer for } // end method outputBarChart public void outputGrades() { System.out.println( "The grades are: " ); System.out.print( " " ); for ( int test = 0; test < grades[ 0 ].length; test++ ) System.out.printf( "Test %d ", test + 1 ); System.out.println( "Average" ); for ( int student = 0; student < grades.length; student++ ) { System.out.printf( "Student %2d", student + 1 ); for ( int test : grades[ student ] ) System.out.printf( "%8d", test ); double average = getAverage( grades[ student ] ); System.out.printf( "%9.2f ", average ); } // end outer for } // end method outputGrades }