我一直在尝试为JUnit 5测试创建一个测试用例，但似乎总是遇到心理障碍。基本上，我有一个程序，从fileInputStream计数单词，然后排序它们。我已经提出的测试用例将验证几个不同单词的计数，但不确定如何使用JUnit 5实现它。我正在尝试测试的代码片段如下所示：

public class wordPopulation {

public static void main(String[] args) throws IOException {

    FileInputStream findIt = new FileInputStream("theraven.txt");
    Scanner fileInput = new Scanner(findIt);

    ArrayList<String> words = new ArrayList<String>();
    ArrayList<Integer> count = new ArrayList<Integer>();

    while (fileInput.hasNext()) {

        String nextWord = fileInput.next();

        if (words.contains(nextWord)) {
            int index = words.indexOf(nextWord);
            count.set(index,  count.get(index)+ 1);
        }
        else {
            words.add(nextWord);
            count.add(1);
        }
    }

    fileInput.close();
    findIt.close();

    for (int i = 0; i < words.size(); ++i) {
        Collections.sort(count, Collections.reverseOrder());

        try(FileWriter fw = new FileWriter("theraven.txt", true);
                BufferedWriter bw = new BufferedWriter(fw);
                PrintWriter out = new PrintWriter(bw)) {

            out.println();
            out.println(words.get(i) + " occurred " + count.get(i) + " times ");

        } catch (IOException e) {
        }
    }
}

}