为printPrimes()方法画控制流程图。
考虑测试用例t1=(n=3)和t2=(n=5)。即使这些测试用例游历printPrimes()方法中相同的主路径，他们不一定找出相同的错误。设计一个简单的错误，使得t2比t1更容易发现。
数组越界错误。
针对printPrimes(),找到一个测试用例，使得响应的测试路径访问连接while语句开始到for语句的边，而不用通过while循环体。
n=0或者n=1
针对printPrimes（）的图例列举每个节点覆盖，边覆盖和主路径覆盖的测试需求。
点覆盖：[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]
边覆盖：[(1,2),(2,3),(3,4),(4,5),(5,6),(6,7),(7,5),(6,8),(8,9),(5,9),(9,10),(10,11),(11,2),(2,12),(12,13),(13,14),(14,15),(15,13),(13,16)]
主路径覆盖：
[1,2,3,4,5,6,7]
[1,2,3,4,5,9,10,11]
[1,2,3,4,5,9,11]
[1,2,3,4,5,6,8,9,10,11]
[1,2,3,4,5,6,8,9,11]
[1,2,12,13,14,15]
[1,2,12,13,16]
[2,3,4,5,6,8,9,10,11,2]
[2,3,4,5,6,8,9,11,2]
[2,3,4,5,9,10,11,2]
[2,3,4,5,9,11,2]
[3,4,5,6,7] 跟上面重复，3打头的这条路跟1开头的最大区别就是可以回2
[3,4,5,6,8,9,10,11,2,12,13,14,15]
[3,4,5,6,8,9,10,11,2,12,13,16]
[3,4,5,6,8,9,11,2,12,13,14,15]
[3,4,5,6,8,9,11,2,12,13,16]
[3,4,5,9,10,11,2,12,13,14,15]
[3,4,5,9,11,2,12,13,14,15]
[3,4,5,9,10,11,2,12,13,16]
[3,4,5,9,11,2,12,13,16]
[5,6,7,5]
[6,7,5,6]？？？ 不是很清楚这算不算一条主路径
[6,7,5,9,10,11,2,12,13,14,15]
[6,7,5,9,11,2,12,13,14,15]
[6,7,5,9,10,11,2,12,13,16]
[6,7,5,9,11,2,12,13,16]
[13,14,15,13]
[14,15,13,16]
实现主路径覆盖，以其中两条为例，具体代码以传至git。
https://github.com/eVonneDingJW/printPrimes
1、全覆盖
2、未全覆盖
