Main Method to be used by Test Class

Hi so i have my main class but im having trouble figuring out how to output my code from my test class. I dont understand even though tried many ways how to output the simple addition and subtraction of two fractions as it should do in my main method but can't seem to get it into my test class.

here is my code for the class with all the functions:

package rational;

 public class Rational {

private int numer, denom;

 //constructors
    public Rational(){
        int num = 1;
        int den = 2;
        reduce();
    }
    public Rational(int num, int den){
    numer = num;
    denom = den;
    reduce();
    }
    public Rational(Rational x){
    numer = x.numer;
    denom = x.denom;
    reduce();
    }

   //setters
    public void setNumer(int num){
    numer = num;
    reduce();
    }
    public void setDenom(int den){
    denom = den;
    reduce();
    }
    public void setRational(int num, int den){
    numer = num;
    denom = den;
    reduce();
    }

     //getters
    public int getNumer(){
    return numer;
    }
    public int getDenom(){
    return denom;
    }

    //Copy method
    public void copyFrom(Rational x){
    numer = x.numer;
    denom = x.denom;
    reduce();
    }

    //Equals method        
    public boolean equals(Rational x){
    if (numer / denom == x.numer / x.denom){
    return(true);
            }
    else {
    return(false);
        }
    }

    //Compare to method
    public int compareTo(Rational x){
    if (numer / denom == x.numer / x.denom){
    return (0);
    }
    else if (numer / denom < x.numer / x.denom){
    return (-1);
    }
    else{
    return (1);
        }    
    }

    //Find greatest common divisor
    static int gcd(int x, int y){
    int r;
    while (y != 0) {
    r = x % y;
    x = y;
    y = r;
        }
    return x;
    }

    //Rational Addition            
    public void plus(Rational x){
    int greatdenom = x.denom * denom;       
    int multx = greatdenom / x.denom;
    int mult = greatdenom / denom;
    denom = x.denom * denom;
    numer = (x.numer * multx) + (numer * mult);
    reduce();
    }

    //Rational Subtraction
    public void minus(Rational x){
    int greatdenom = x.denom * denom;       
    int multx = greatdenom / x.denom;
    int mult = greatdenom / denom;
    denom = x.denom * denom;
    if (x.numer > numer){
    numer = (x.numer * multx) - (numer * mult);
        }
    else {
    numer = (numer * mult) - (x.numer * multx);
        }
    reduce();
    }

     //Multiplication       
    public void times(Rational x){
    numer = numer * x.numer;
    denom = denom * x.denom;
    reduce();
    }

    //Division        
    public void divBy(Rational x){
    numer = numer / x.numer;
    denom = denom / x.denom;
    reduce();
    }

     //Fraction simplifier        
    private void reduce(){
    int divisor;
    divisor = Rational.gcd(numer, denom);
    numer = numer / divisor;
    denom = denom / divisor;
    }

@Override
    public String toString(){
    if (denom == 1){
    return numer + "";
    }
    else{
    return numer + " / " + denom;
    }       
}
   }