Question

 YOU MUST NOT MAKE ANY CHANGES TO THAT CODE
package edu.buffalo.cse116;

/**
 * Class that can be used to test if two integers are coprime. Numbers are considered coprime iff the largest divisor
 * shared by both numbers is 1. Identifying coprime (also called relatively prime) numbers is valuable for RSA public
 * key cryptography (and possibly other things, but the author has never seen any other uses).
 */
public class CoprimeNumbers {

  /**
   * Given two integers, this returns true if they are relatively prime and false if they are not. Based upon the first
   * webpage I found ({@link "https://primes.utm.edu/notes/faq/negative_primes.html"}), the primality of negative
   * numbers is up for debate. This method will not treat negatives differently.
   *
   * @param a First integer to be tested
   * @param b Second integer to be tested
   * @return True when the greatest common divisor of these numbers is 1; false otherwise.
   */
  public boolean isCoprime(int a, int b) {
    // Continue using Euclid's algorithm until we find a common divisor
    while (b != 0) {
      // Remember b's value
      int temp = b;
      // Set b to the remainder of dividing a by b (e.g., a mod b).
      b = a % b;
      // Set a equal to b's old value.
      a = temp;
    }
    // The gcd is the value in a. If this is 1 the numbers are coprime.
    if (a == 1) {
      return true;
    }
    // When they are not 1, they have a common divisor.
    else {
      return false;
    }
  }
}

QUESTION:

write a class, named CoprimeNumbersTest and in the edu.buffalo.cse116 package which contains JUnit test cases validating my code works (e.g., your tests will execute all the lines in my code). Because this is important, I reiterate your solution must test my unchanged CoprimeNumbers.java file.

Answer 1

Here is the Junit test for your class. It tests for various combinations when b=0 , b=1, a>b , a<b and a=b. You can just run it in eclipse by right click and Run as Junit Test. Since the return value from your code is eithertrue or false, we just use assertTrue() or assertFalse().

package edu.buffalo.cse116;

import static org.junit.Assert.*;

import org.junit.Test;

public class CoprimeNumbersTest {
   CoprimeNumbers cpn= new CoprimeNumbers();
  
   @Test
   public void test1()
   {
       //Test when a = b
       boolean b=cpn.isCoprime(10, 10);
       assertFalse(b);
   }
  
   @Test
   public void test2()
   {
       //Test when b=1
       boolean b=cpn.isCoprime(7, 1);
       assertTrue(b);
   }
  
   @Test
   public void test3()
   {
       //Test when b=0
       boolean b=cpn.isCoprime(7, 0);
       assertFalse(b);
   }
  
  
   @Test
   public void test4()
   {
       //Test when a < b
       boolean b=cpn.isCoprime(5,7);
       assertTrue(b);
   }
   @Test
   public void test5()
   {
       //Test when a > b
       boolean b=cpn.isCoprime(13, 11);
       assertTrue(b);
   }
}

workspace - <Java-lestava/src/edu/buffalo/csell6/CoprimeNumbers lest.java - Eclipse File Edit Source Refactor Navigate Search Project Run Window Help Package Ex.Project Exp... iiCoprimeNumbersTest.java 3CoprimeNumbers.java 1 package edu.buffalo.cse116; 2 3e import static org.junit.Assert.*; Finished after 0.042 seconds Runs: 5/5 Errors: Failures: 4 5 import org.junit.Test; 6 7 public class CoprimeNumbersTest 9 e @Test 12 E.buffalo.cse116.CoprimeNumbersTest [Runner: JUnit 4]8 CoprimeNumbers cpn- new CoprimeNumbers (); test1 (0.001 s) test2 (0.001s) test3 (0.001s) test4 (0.001s) test5 (0.002 s) 10e public void test1() //Test when ab boolean b-cpn.isCoprime (10, 10); assertFalse(b); 13 15 16 17 18 @Test 19 20 21 public void test2() //Test when b-1 boolean b-cpn.isCoprime(7, 1); assertTrue(b); 23 24 25 26 @Test 27 28 Failure Trace public void test3()