软件测试中出现私有方法时，需要使用反射机制来实现代码的测试。
首先，简略说一下反射是什么~~https://www.cnblogs.com/zhaoguhong/p/6937364.html
COPY——JAVA反射机制是在运行状态中，对于任意一个类，都能够知道这个类的所有属性和方法；对于任意一个对象，都能够调用它的任意方法和属性；这种动态获取信息以及动态调用对象方法的功能称为java语言的反射机制。
其次，代码~~
被测试类：
public class MSD { private static final int BITS_PER_BYTE = 8; private static final int BITS_PER_INT = 32; // each Java int is 32 bits private static final int R = 256; // extended ASCII alphabet size private static final int CUTOFF = 15; // cutoff to insertion sort // do not instantiate private MSD() { } //private MSD(int a) { } /** * Rearranges the array of extended ASCII strings in ascending order. * * @param a the array to be sorted */ public static void sort(String[] a) { int n = a.length; String[] aux = new String[n]; sort(a, 0, n-1, 0, aux); } // return dth character of s, -1 if d = length of string private static int charAt(String s, int d) { assert d >= 0 && d <= s.length(); if (d == s.length()) return -1; return s.charAt(d); } // sort from a[lo] to a[hi], starting at the dth character //sort(a, 0, n-1, 0, aux); private static void sort(String[] a, int lo, int hi, int d, String[] aux) { // cutoff to insertion sort for small subarrays if (hi <= lo + CUTOFF) { insertion(a, lo, hi, d); return; } // compute frequency counts int[] count = new int[R+2]; for (int i = lo; i <= hi; i++) { int c = charAt(a[i], d); count[c+2]++; } // transform counts to indicies for (int r = 0; r < R+1; r++) count[r+1] += count[r]; // distribute for (int i = lo; i <= hi; i++) { int c = charAt(a[i], d); aux[count[c+1]++] = a[i]; } // copy back for (int i = lo; i <= hi; i++) a[i] = aux[i - lo]; // recursively sort for each character (excludes sentinel -1) for (int r = 0; r < R; r++) sort(a, lo + count[r], lo + count[r+1] - 1, d+1, aux); } // insertion sort a[lo..hi], starting at dth character private static void insertion(String[] a, int lo, int hi, int d) { for (int i = lo; i <= hi; i++) for (int j = i; j > lo && less(a[j], a[j-1], d); j--) exch(a, j, j-1); } // exchange a[i] and a[j] private static void exch(String[] a, int i, int j) { String temp = a[i]; a[i] = a[j]; a[j] = temp; } // is v less than w, starting at character d private static boolean less(String v, String w, int d) { // assert v.substring(0, d).equals(w.substring(0, d)); for (int i = d; i < Math.min(v.length(), w.length()); i++) { if (v.charAt(i) < w.charAt(i)) return true; if (v.charAt(i) > w.charAt(i)) return false; } return v.length() < w.length(); } /** * Rearranges the array of 32-bit integers in ascending order. * Currently assumes that the integers are nonnegative. * * @param a the array to be sorted */ public static void sort(int[] a) { int n = a.length; int[] aux = new int[n]; sort(a, 0, n-1, 0, aux); } // MSD sort from a[lo] to a[hi], starting at the dth byte private static void sort(int[] a, int lo, int hi, int d, int[] aux) { // cutoff to insertion sort for small subarrays if (hi <= lo + CUTOFF) { insertion(a, lo, hi, d); return; } // compute frequency counts (need R = 256) int[] count = new int[R+1]; int mask = R - 1; // 0xFF; int shift = BITS_PER_INT - BITS_PER_BYTE*d - BITS_PER_BYTE; for (int i = lo; i <= hi; i++) { int c = (a[i] >> shift) & mask; count[c + 1]++; } // transform counts to indicies for (int r = 0; r < R; r++) count[r+1] += count[r]; /************* BUGGGY CODE. // for most significant byte, 0x80-0xFF comes before 0x00-0x7F if (d == 0) { int shift1 = count[R] - count[R/2]; int shift2 = count[R/2]; for (int r = 0; r < R/2; r++) count[r] += shift1; for (int r = R/2; r < R; r++) count[r] -= shift2; } ************************************/ // distribute for (int i = lo; i <= hi; i++) { int c = (a[i] >> shift) & mask; aux[count[c]++] = a[i]; } // copy back for (int i = lo; i <= hi; i++) a[i] = aux[i - lo]; // no more bits if (d == 4) return; // recursively sort for each character if (count[0] > 0) sort(a, lo, lo + count[0] - 1, d+1, aux); for (int r = 0; r < R; r++) if (count[r+1] > count[r]) sort(a, lo + count[r], lo + count[r+1] - 1, d+1, aux); } // TODO: insertion sort a[lo..hi], starting at dth character private static void insertion(int[] a, int lo, int hi, int d) { for (int i = lo; i <= hi; i++) for (int j = i; j > lo && a[j] < a[j-1]; j--) exch(a, j, j-1); } // exchange a[i] and a[j] private static void exch(int[] a, int i, int j) { int temp = a[i]; a[i] = a[j]; a[j] = temp; } }
测试类：
public class MSDTest { String[] a1 = {"a","c","b"}; String[] a2 = {"","b","c"}; String[] a3 = {"a","c","b","a","c","b","a","c","b","a","c","b","a","c","b","a","c","b"}; String[] a4 = {"avd","db","zc","radd","b","sascsa","a","b","c","a","b","c","a","b","c","a","b","c"}; String[] a5 = {"z","c","d","a","f","b","a","c","v","a","c","a","a","c","b","a","c","b"}; String[] a6 = {"zza","zcb"}; int[] b1 = {3,2,1}; int[] b2 = {1,2,3,4,5,2,4,5,6,22,1,12,2,222,22,4,7}; int[] b3 = {}; @Test //私有的构造方法 私有的函数 public void testSortString() throws Exception { // 得到Class Class<MSD> class1 = MSD.class; // 获取不带参数的构造方法 Constructor constructor=class1.getDeclaredConstructor(); //设置为可访问 constructor.setAccessible(true); //创建实例 Object instance=(Object)constructor.newInstance(); Method method=class1.getDeclaredMethod("charAt", new Class[] {String.class,int.class}); //将方法设为可执行 method.setAccessible(true); //反射机制调用方法的返回值是一个对象 Object result = method.invoke(instance, new Object[]{"",0}); assertEquals(-1, result); Method method1=class1.getDeclaredMethod("sort", new Class[] {int[].class,int.class,int.class,int.class,int[].class}); //将方法设为可执行 method1.setAccessible(true); //反射机制调用方法的返回值是一个对象 //method1.invoke(instance, new Object[]{b2,0,6,4,b3}); Object result1 = method1.invoke(instance, new Object[]{b2,0,10,4,b3}); MSD.sort(a1); MSD.sort(a2); MSD.sort(a3); MSD.sort(a4); MSD.sort(a5); MSD.sort(a6); MSD.sort(b1); MSD.sort(b2); } @Test public void testSortInt() { String[] a = {"1"}; MSD.sort(a); } }
这个代码中，被测试类的构造方法是私有、无参的，里面被测试的方法也是私有的。
如果被测试方法不是私有的，testToString中部分代码可改为：
// 得到Class Class clazz = Class.forName("net.mooctest.MSD"); // 获取带参数的构造方法 Constructor con = clazz.getDeclaredConstructor(int.class); //设置为可访问 con.setAccessible(true); MSD s = (MSD) con.newInstance(18); //获取类中的带参方法(public方法) Method method=clazz.getMethod("sort", int[].class); //调用带参方法 method.invoke(s,b1);
如果构造方法不是私有时，可以这样写：
//获取类 Class clazz = Class.forName("net.mooctest.BPlusTree"); //获取带参数的类构造方法 Constructor con1 = clazz.getDeclaredConstructor(int.class); Constructor con2 = clazz.getDeclaredConstructor(int.class,int.class); //设置为可访问 con1.setAccessible(true); con2.setAccessible(true); //创建实例 //BPlusTree BP = (BPlusTree) con1.newInstance(3); //获取方法 Method method = clazz.getDeclaredMethod("findLeaf", int.class); //设置方法为可访问 method.setAccessible(true); //反射机制中返回值是一个对象 //Object obj = method.invoke(bp1, 1); Object obj2 = method.invoke(bp2, 1);
其中原因不明~~~