如何编写JUnit测试用例以查找流中的第一个非重复字符？

Question

由于用户更多地关注较小的漏洞而不是要求，因此，我给出了需要junit测试用例的实际工作代码（替换）。

import java.util.*;

public class FirstNonRepeatingCharacterStream {

    List<Character> chars = new ArrayList<>();
    boolean[] repeated = new boolean[256];

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        FirstNonRepeatingCharacterStream tester = 
                new FirstNonRepeatingCharacterStream();
        while (true) {
            Character ch = new Character(sc.next().charAt(0));
            Character output = tester.firstNonRepeatingCharStream1(ch);
            System.out.println(output);
        }
    }

    public Character firstNonRepeatingCharStream1(Character x) {

        if (x == null) {
            return x;
        }

        Character output = null;

        if (!repeated[x]) {
            if (!chars.contains(x)) {
                chars.add(x);
            } else {
                chars.remove(new Character(x));
                repeated[x] = true;
            }
        }
        if (chars.size() != 0) {
            output = new Character(chars.get(0));
        }
        return output;

    }

}

User enters one character at a time.
input a -> output a
input b -> that means input ab as it's stream -> output a
input a -> that means input aba as it's stream -> output b
input c -> that means input abac as it's stream -> output b
input b -> that means input abacb as it's stream -> output c
input a -> that means input abacba as it's stream -> output c
input d -> that means input abacbad as it's stream -> output c

请让我知道如何编写应符合主要方法的单元测试。 在junit测试用例中不需要while循环。

提前致谢。

Answer 1

听起来这可能主要归结为提出“平均”测试字符串以尝试击中代码中的各种边缘情况：

String testStrings[] {
    null,
    "", // empty string
    "a", // easiest possible string with a match
    "aa", // easiest possible string with no match
    "aba", // slightly less easy string with a match
    "aaaaa", // no match on N instances of a character
    "aaaaab", // match on end of N instances of a character
    "baaaaa", // match at beginning of N instances of a character
    "aabaaa", // match in the middle of N instances of a character
    "abcdefghijklmnopqrstuvwxyzyxwvutsrqponmlkjihgfedcba", // harder string where the unique letter is in the middle (z)
    "abcdefghijklmnopqrstuvwxyzzyxwvutsrqponmlkjihgfedcb", // harder string where the unique character is at the front (a)
    "bcdefghijklmnopqrstuvwxyzzyxwvutsrqponmlkjihgfedcba", // harder string where the unique character is at the back
    "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxy" // other harder string... etc.
};

然后，您将开发出类似的预期输出数组，然后在单个for(int i = 0;...)循环中浏览所有案例。

开发测试输入的另一种方法是通过算法生成测试字符串，以使所有字符以三种策略（aabbcc，abccba，abcabc）之一成对出现，然后拨出第一个字符，然后是最后一个字符，然后是一个中间（您先检查要删除的字符，然后将其作为测试值）。

有很多不同的方法可以给这只猫蒙皮。

PS：您当前的代码将以null或任何“整数”值大于255的字符中断。在那里出现了许多怪异的Unicode字符...我似乎还记得，听说现在有几种null和虚构的语言都使用Unicode（古埃及语） ，JJR Tolkien的Elvish，Klingon等），更不用说CJKV范围了（中文，日文，韩文，越南文）。 超过256个的“代码点”很多。

Answer 2

我自己解决了。

class FirstNonRepeatingCharacterStreamTest3 {

    private static FirstNonRepeatingCharacterStream tester;

    @BeforeAll
    static void setUpBeforeClass() throws Exception {
        tester = new FirstNonRepeatingCharacterStream();
    }

    @DisplayName("MyTest")
    @ParameterizedTest(name = "{index} => input={0}, output= {1}")
    @CsvSource({
        "'a', 'a'",
        "'b', 'a'",
        "'a', 'b'",
        "'c', 'b'",
        "'b', 'c'",
        "'a', 'c'",
        "'d', 'c'"
    })
    public void testFirstNonRepeatingCharStream101(Character input, Character output) {
        Character actual = tester.firstNonRepeatingCharStream1(input);
        assertEquals(output, actual);
    }
}