java - 一个 JUnit 如何测试交互式的、基于文本的 Java 应用程序？

Question

理想情况下，我想编写 JUnit 测试代码，以交互方式测试学生基于文本的 I/O 应用程序。使用 System.setIn()/.setOut() 会导致问题，因为底层流正在阻塞。 Birkner 的系统规则 (http://www.stefan-birkner.de/system-rules/index.html) 在较早的帖子 (Testing console based applications/programs - Java) 中被推荐，但它似乎要求在运行单元测试目标之前提供所有标准输入，因此不是交互式的。

要提供具体的测试目标示例，请考虑这个猜谜游戏代码:

public static void guessingGame() {
    Scanner scanner = new Scanner(System.in);
    Random random = new Random();
    int secret = random.nextInt(100) + 1;
    System.out.println("I'm thinking of a number from 1 to 100.");
    int guess = 0;
    while (guess != secret) {
        System.out.print("Your guess? ");
        guess = scanner.nextInt();
        final String[] responses = {"Higher.", "Correct!", "Lower."};
        System.out.println(responses[1 + new Integer(guess).compareTo(secret)]);
    }
}

现在想象一个 JUnit 测试，它将提供猜测、读取响应并玩游戏直到完成。如何在 JUnit 测试框架中实现这一目标？

回答:

使用下面Andrew Charneski推荐的方法，添加输出刷新(包括在上面的每个打印语句后添加System.out.flush();)，非随机播放，恢复System. in/out，这段代码似乎执行了我想象中的测试:

@Test
public void guessingGameTest() {
    final InputStream consoleInput = System.in;
    final PrintStream consoleOutput = System.out;
    try {
        final PipedOutputStream testInput = new PipedOutputStream();
        final PipedOutputStream out = new PipedOutputStream();
        final PipedInputStream testOutput = new PipedInputStream(out);
        System.setIn(new PipedInputStream(testInput));
        System.setOut(new PrintStream(out));
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    PrintStream testPrint = new PrintStream(testInput);
                    BufferedReader testReader = new BufferedReader(
                            new InputStreamReader(testOutput));
                    assertEquals("I'm thinking of a number from 1 to 100.", testReader.readLine());
                    int low = 1, high = 100;
                    while (true) {
                        if (low > high)
                            fail(String.format("guessingGame: Feedback indicates a secret number > %d and < %d.", low, high));
                        int mid = (low + high) / 2;
                        testPrint.println(mid);
                        testPrint.flush();
                        System.err.println(mid);
                        String feedback = testReader.readLine();
                        if (feedback.equals("Your guess? Higher."))
                            low = mid + 1;
                        else if (feedback.equals("Your guess? Lower."))
                            high = mid - 1;
                        else if (feedback.equals("Your guess? Correct!"))
                            break;
                        else
                            fail("Unrecognized feedback: " + feedback);
                    }
                } catch (IOException e) {
                    e.printStackTrace(consoleOutput);
                } 
            }
        }).start();
        Sample.guessingGame();
    }
    catch (IOException e) {
        e.printStackTrace();
        fail(e.getMessage());
    }
    System.setIn(consoleInput);
    System.setOut(consoleOutput);
}

Answer 1

使用 PipedInput/OutputStream，例如

    final PrintStream consoleOutput = System.out;
    final PipedOutputStream testInput = new PipedOutputStream();
    final PipedOutputStream out = new PipedOutputStream();
    final PipedInputStream testOutput = new PipedInputStream(out);
    System.setIn(new PipedInputStream(testInput));
    System.setOut(new PrintStream(out));
    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                PrintStream testPrint = new PrintStream(testInput);
                BufferedReader testReader = new BufferedReader(
                    new InputStreamReader(testOutput));
                while (true) {
                    testPrint.println((int) (Math.random() * 100));
                    consoleOutput.println(testReader.readLine());
                }
            } catch (IOException e) {
                e.printStackTrace(consoleOutput);
            }
        }
    }).start();
    guessingGame();