四、编写JUnit测试（Writing a Test with JUnit）

编写JUnit测试，只要扩展junit.framework.TestCase类可以了。你的TestCase子类将按你希望的顺序调用test cases，包括可能的测试前设置和测试后清除。设置在setUp方法中进行。清除在tearDown方法中进行。你可以，但不是必须，重载这两个方法做你想做的事。

下面是对上面的例子用JUnit进行重写的test case：

程序列表3 (CalculatorTest.java， taken from CalculatorTest.java.v2):

import junit.framework.TestCase;

public class CalculatorTest extends TestCase {

  private FactorCalculator calc;

  public CalculatorTest(String name) {
    super(name);
  }

  protected void setUp() {
    calc = new FactorCalculator();
  }

  public void testFactor() {
    int numToFactor;
    int[] factorArray;
    int[] correctFactorArray;

    numToFactor = 100;
    factorArray = calc.factor(numToFactor);
    correctFactorArray = new int[] {2， 2， 5， 5};
    assertTrue("bad factorization of " + numToFactor， isSameFactorArray(factorArray， correctFactorArray));

    numToFactor = 4;
    factorArray = calc.factor(numToFactor);
    correctFactorArray = new int[] {2， 2};
    assertTrue("bad factorization of " + numToFactor， isSameFactorArray(factorArray， correctFactorArray));

    numToFactor = 3;
    factorArray = calc.factor(numToFactor);
    correctFactorArray = new int[] {3};
    assertTrue("bad factorization of " + numToFactor， isSameFactorArray(factorArray， correctFactorArray));

    numToFactor = 2;
    factorArray = calc.factor(numToFactor);
    correctFactorArray = new int[] {2};
    assertTrue("bad factorization of " + numToFactor， isSameFactorArray(factorArray， correctFactorArray));
  }

  // presumes both factor arrays are in numeric order
  private boolean isSameFactorArray(int[] factorArray1， int[] factorArray2) {
    boolean isSame = false;
    if (factorArray1.length == factorArray2.length) {
      isSame = true;
      for(int i = 0; i < factorArray1.length; i++) {
        if (factorArray1[i] != factorArray2[i]) {
          isSame = false;
          break;
        }
      }
    }
    return isSame;
  }

  public void testIsPrime() {
    int numToCheck;
    boolean isPrime;

    numToCheck = 2;
    isPrime = calc.isPrime(numToCheck);
    assertTrue("bad isPrime value for " + numToCheck， isPrime);

    numToCheck = 3;
    isPrime = calc.isPrime(numToCheck);
    assertTrue("bad isPrime value for " + numToCheck， isPrime);

    numToCheck = 4;
    isPrime = calc.isPrime(numToCheck);
    assertFalse("bad isPrime value for " + numToCheck， isPrime);

    try {
      numToCheck = 1;
      isPrime = calc.isPrime(numToCheck);
      fail("isPrime should throw exception for numbers less than 2");
    } catch (IllegalArgumentException e) {
      // do nothing because throwing IAE is the proper action
    }
  }

  public void testIsDivisor() {
    int numToCheck;
    int potentialDivisor;
    boolean isDivisor;

    numToCheck = 6;
    potentialDivisor = 3;
    isDivisor = calc.isDivisor(numToCheck， potentialDivisor);
    assertTrue("bad isDivisor value for (" + numToCheck + "， " + potentialDivisor + ")"， isDivisor);

    numToCheck = 5;
    potentialDivisor = 2;
    isDivisor = calc.isDivisor(numToCheck， potentialDivisor);
    assertFalse("bad isDivisor value for (" + numToCheck + "， " + potentialDivisor + ")"， isDivisor);

    try {
      numToCheck = 6;
      potentialDivisor = 0;
      isDivisor = calc.isDivisor(numToCheck， potentialDivisor);
      fail("isDivisor should throw an exception when potentialDivisor is 0 but did not");
    } catch (ArithmeticException e) {
      // do nothing because throwing AE is the proper action
    }
  }
}