printPrime（）的测试

程序结构如下：

package com.prime;

public class Prime {
    public static Boolean isDivisable(int prime, int curPrime) {
        if (curPrime % prime == 0) {
            return true;
        } else
            return false;
    }

    public static void printPrimes(int n) {
        int curPrime; // Value currently considered for primeness
        int numPrimes; // Number of primes found so far.
        boolean isPrime; // Is curPrime prime?
        int[] primes = new int[100]; // The list of prime numbers.

        // Initialize 2 into the list of primes.
        primes[0] = 2;
        numPrimes = 1;
        curPrime = 2;
        while (numPrimes < n) {
            curPrime++; // next number to consider ...
            isPrime = true;
            for (int i = 0; i <= numPrimes - 1; i++) { // for each previous
                                                        // prime.
                if (isDivisable(primes[i], curPrime)) { // Found a divisor,
                                                        // curPrime is not
                                                        // prime.
                    isPrime = false;
                    break; // out of loop through primes.
                }
            }
            if (isPrime) { // save it!
                primes[numPrimes] = curPrime;
                numPrimes++;
            }
        } // End while

        // Print all the primes out.
        for (int i = 0; i <= numPrimes - 1; i++) {
            System.out.println("Prime: " + primes[i]);
        }
    } // end printPrimes
}

a）程序的控制流图

b）将程序中的n用3替换，比如while循环里的 numPrimes<n 改成numPrimes<3 这样如果测试用例是n=3就不会发现错误，但是如果是n=5就能很快发现错误。

c）让n=1即可。

d）节点覆盖：

TR={1,2,3,4,5,6,7,8,9,10,11,12,13};

边覆盖：

TR={(1,2),(2,3),(2,10),(3,4),(4,5),(4,8),(5,6),(5,7),(6,8),(7,4),(8,2),(8,9),(9,2),(10,11),(11,12),(11,13),(12,11)};

主路径覆盖：

TR={(1,2,3,4,8,9),(1,2,3,4,5,7),(1,2,3,4,5,6,8,9),(1,2,10,11,12),(1,2,10,11,13),

(2,3,4,8,9,2),(2,3,4,8,2),(2,3,4,5,7),(2,3,4,5,6,8,9,2),(2,3,4,5,6,8,2),(2,10,11,12),(2,10,11,13),

(3,4,5,6,8,9,2,3),(3,4,5,6,8,2,3),(3,4,8,9,2,3),(3,4,8,2,3),(3,4,5,6,8,9,2,10,11,12),(3,4,5,6,8,2,10,11,12),(3,4,5,6,8,9,2,10,11,13),(3,4,5,6,8,2,10,11,13),(3,4,8,9,2,10,11,12),(3,4,8,2,10,11,12),(3,4,8,9,2,10,11,13),(3,4,8,2,10,11,13),

(4,5,7,4),(4,5,6,8,9,2,3,4),(4,5,6,8,2,3,4),(4,8,9,2,3,4),(4,8,2,3,4),

(5,7,4,5),(5,6,8,9,2,3,4,5),(5,6,8,2,3,4,5),

(6,8,9,2,3,4,5,6),(6,8,9,2,3,4,5,6),(6,8,9,2,3,4,5,7),(6,8,2,3,4,5,7),

(7,4,5,7),(7,4,8,9,2,3),(7,4,8,2,3),(7,4,5,6,8,9,2,3),(7,4,5,6,8,2,3),(7,4,5,6,8,9,2,10,11,12),(7,4,5,6,8,9,2,10,11,13),(7,4,5,6,8,2,10,11,12),(7,4,5,6,8,2,10,11,13),(7,4,8,9,2,10,11,12),(7,4,8,9,2,10,11,13),(7,4,8,2,10,11,12),(7,4,8,2,10,11,13),

(8,2,3,4,8),(8,9,2,3,4,8),(8,2,3,4,5,6,8),(8,9,2,3,4,5,6,8),

(9,2,3,4,8,9),(9,2,3,4,5,6,8,9),

(11,12,11),

(12,11,12),(12,11,13)}.

 

设计junit测试代码如下：

package com.prime;

import static org.junit.Assert.*;

import java.io.ByteArrayOutputStream;
import java.io.PrintStream;

import org.junit.Before;
import org.junit.Test;

public class PrimeTest {
    Prime prime;
    ByteArrayOutputStream baos;
    
    @Before
    public void setUp() throws Exception {
        prime = new Prime();
        baos = new ByteArrayOutputStream();
        System.setOut(new PrintStream(baos));
    }

    @Test
    public void testPrintPrimes() {
        String outcome = new String("Prime: 2\r\nPrime: 3\r\nPrime: 5\r\nPrime: 7\r\nPrime: 11\r\n");
        prime.printPrimes(5);
        assertEquals(outcome, baos.toString()); 
    }

}

程序将输出的控制台的数据流重定向到另外的新的打印流，也就是我们提前设置的字节输出流内，然后将它与我们设想的输出字符串比较。结果如下