java - 写入文件的 JUnit 测试在本地通过但在 Travis CI 上失败

Question

问题

老师指示我和我的小组成员为我们的游戏实现一个记录器。这个记录器应该用 JUnit 进行很好的测试，所以我们做到了。我们现在正在处理的一个问题是，所有这些测试都在本地通过，但在 Travis CI 上时不时地失败。

我们的分析

我们怀疑这些测试没有足够的时间在执行断言之前实际创建和删除日志文件。但是，我们不确定这是否是导致我们的测试在 Travis 上失败的原因。

我们的代码

Logger.java

package logging;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.StandardCopyOption;
import java.sql.Timestamp;
import java.util.Calendar;

public final class Logger extends Thread {
    private static volatile boolean debug = false;
    private static volatile StringBuilder queue = new StringBuilder();
    private static volatile File file = new File("log.log");
    private static volatile int logLength = 10000;
    private static Logger logger;

    /**
     * supported logging types.
     *
     */
    public enum LogType {
        INFO, WARNING, ERROR
    }

    private Logger() {
    } // unreachable because static

    /**
     * The logger runs in his own thread to prevent concurrent writing
     * exceptions on the log file if multiple threads are logging.
     */
    public void run() {
        while (debug) {
            try {
                sleep(10000);
                if (queue.length() > 0) {
                    try {
                        writeToFile();
                    } catch (IOException exception) {
                        exception.printStackTrace();
                    }
                }
            } catch (InterruptedException exception) {
                exception.printStackTrace();
            }
        }
    }

    private void writeToFile() throws IOException {
        if (!file.exists()) {
            file.createNewFile();
        }
        FileWriter writer = new FileWriter(file, true);
        writer.write(queue.toString());
        writer.close();
        capFileSize();
    }

    private void capFileSize() throws IOException {
        int fileLength = countLines();
        if (fileLength > logLength) {
            String line;
            File tempFile = File.createTempFile("TETRIS_LOG_", ".log");
            BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));
            try {
                BufferedReader reader = new BufferedReader(new FileReader(file));
                try {
                    skipLines(fileLength - logLength, reader);
                    while ((line = reader.readLine()) != null) {
                        writer.write(line);
                        writer.newLine();
                    }
                } finally {
                    reader.close();
                }
            } finally {
                writer.close();
            }
            Files.move(tempFile.toPath(), file.toPath(), StandardCopyOption.REPLACE_EXISTING);
        }
    }

    private void skipLines(int lines, BufferedReader file) throws IOException {
        for (int i = 0; i < lines; i++) {
            file.readLine();
        }
    }

    private int countLines() throws IOException {
        char[] buffer = new char[1024];
        int count = 0;
        int readChars = 0;
        boolean empty = true;
        BufferedReader reader = new BufferedReader(new FileReader(file));
        try {
            while ((readChars = reader.read(buffer)) != -1) {
                empty = false;
                for (int i = 0; i < readChars; ++i) {
                    if (buffer[i] == '\n') {
                        ++count;
                    }
                }
            }
            return (count == 0 && !empty) ? 1 : count;
        } finally {
            reader.close();
        }
    }

    /**
     * Log lets you log a line in the log file, conditional on the debug mode
     * being on.
     * 
     * @param sender
     *            the object invoking the log statement
     * @param logtype
     *            the log type, for homogeneity constrained in the LogType enum
     * @param message
     *            the message that is logged
     */
    public static void log(Object sender, LogType logtype, String message) {
        if (debug) {
            String msg = String.format("[%s] message @[%s] from object %s: %s\r\n",
                logtype.toString(),
                new Timestamp(Calendar.getInstance().getTimeInMillis()).toString(),
                sender.toString(), message);
            queue.append(msg);
        }
    }

    public static void info(Object sender, String message) {
        Logger.log(sender, LogType.INFO, message);
    }

    public static void error(Object sender, String message) {
        Logger.log(sender, LogType.ERROR, message);
    }

    public static void warning(Object sender, String message) {
        Logger.log(sender, LogType.WARNING, message);
    }

    /**
     * clearLog truncates the log, in case you accidentally logged a nude
     * picture or something.
     */
    public static void clearLog() {
        try {
            Files.deleteIfExists(file.toPath());
        } catch (IOException exception) {
            exception.printStackTrace();
        }
    }

    /* getters / setters */
    public static int getLogLength() {
        return logLength;
    }

    public static void setLogLength(int length) {
        logLength = length;
    }

    public static void setLogDir(String path) {
        file = new File(path);
    }

    public static String getLogDir() {
        return file.toString();
    }

    /**
     * switch debug on.
     */
    public static synchronized void setDebugOn() {
        if (!debug) {
            debug = true;
            logger = new Logger();
            logger.start();
        }
    }

    /**
     * switch debug off.
     */
    public static void setDebugOff() {
        if (debug) {
            debug = false;
            try {
                logger.join();
            } catch (InterruptedException exception) {
                exception.printStackTrace();
            }
        }
        logger = null;
    }
}

LoggerTest.java

package logging;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

import org.junit.Test;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

public class LoggerTest {
    @Test
    public void test_logcreate() {
        String testloc = "test.log";
        Logger.setLogDir(testloc);
        Logger.clearLog();
        Logger.setDebugOn();
        Logger.log(this, Logger.LogType.ERROR, "test 1");
        Logger.setDebugOff();
        assertTrue(new File(testloc).exists());
    }

    @Test
    public void test_logdelete() {
        String testloc = "test.log";
        Logger.setLogDir(testloc);
        Logger.setDebugOn();
        Logger.log(this, Logger.LogType.ERROR, "test 1");
        assertTrue(new File(testloc).exists());
        Logger.setDebugOff();
        Logger.clearLog();
        assertFalse(new File(testloc).exists());
    }

    @Test
    public void test_debugMode() {
        String testloc = "test.log";
        Logger.setLogDir(testloc);
        Logger.setDebugOff();
        Logger.clearLog();
        Logger.log(this, Logger.LogType.ERROR, "test 1");

        assertFalse(new File(testloc).exists());
    }

    @Test
    public void test_capLog() throws IOException, InterruptedException {
        String testloc = "test.log";
        Logger.setLogDir(testloc);
        Logger.setLogLength(10);
        Logger.clearLog();
        Logger.setDebugOn();
        for (int i = 0; i < 100; i++) {
            Logger.log(this, Logger.LogType.ERROR, "test 1");
        }
        Logger.setDebugOff();
        Thread.sleep(1000);
        assertTrue(new File(testloc).exists());

        int count = 0;
        File file = new File(testloc);
        FileReader fileReader = new FileReader(file);
        BufferedReader reader = new BufferedReader(fileReader);
        while (reader.readLine() != null) {
            ++count;
        }
        reader.close();
        assertEquals(10, count);

    }
}

Travis 作业日志

[...]

:test
Download https://jcenter.bintray.com/org/jacoco/org.jacoco.agent/0.7.7.201606060606/org.jacoco.agent-0.7.7.201606060606.pom
Download https://jcenter.bintray.com/org/jacoco/org.jacoco.build/0.7.7.201606060606/org.jacoco.build-0.7.7.201606060606.pom
Download https://jcenter.bintray.com/org/jacoco/org.jacoco.agent/0.7.7.201606060606/org.jacoco.agent-0.7.7.201606060606.jar
tetris.LoggerTest > test_logcreate FAILED
    java.lang.AssertionError at LoggerTest.java:26
tetris.LoggerTest > test_logdelete FAILED
    java.lang.AssertionError at LoggerTest.java:35
47 tests completed, 2 failed
:test FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':test'.

[...]

编辑#1

我用过Awaitility但 Travis 仍在努力创建/删除文件。即使超时一分钟。

LoggerTest.java

package tetris;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.util.concurrent.Callable;

import org.junit.Test;

import static com.jayway.awaitility.Awaitility.with;
import static com.jayway.awaitility.Duration.*;
import static org.hamcrest.Matchers.equalTo;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import logging.Logger;

public class LoggerTest {

    @Test
    public void test_logcreate() throws Exception {
        String testloc = "test.log";
        Logger.setLogDir(testloc);
        Logger.clearLog();
        Logger.setDebugOn();
        Logger.log(this, Logger.LogType.ERROR, "test 1");
        Logger.setDebugOff();

        asyncWaitForFileCreation(testloc);
        assertTrue(new File(testloc).exists());
    }

    @Test
    public void test_logdelete() throws Exception {
        String testloc = "test.log";
        Logger.setLogDir(testloc);
        Logger.setDebugOn();
        Logger.log(this, Logger.LogType.ERROR, "test 1");

        asyncWaitForFileCreation(testloc);
        assertTrue(new File(testloc).exists());

        Logger.setDebugOff();
        Logger.clearLog();

        asyncWaitForFileRemoval(testloc);
        assertFalse(new File(testloc).exists());
    }

    @Test
    public void test_debugMode() throws Exception {
        String testloc = "test.log";
        Logger.setLogDir(testloc);
        Logger.setDebugOff();
        Logger.clearLog();
        Logger.log(this, Logger.LogType.ERROR, "test 1");

        asyncWaitForFileRemoval(testloc);
        assertFalse(new File(testloc).exists());
    }

    @Test
    public void test_capLog() throws Exception {
        String testloc = "test.log";
        Logger.setLogDir(testloc);
        Logger.setLogLength(10);
        Logger.clearLog();
        Logger.setDebugOn();
        for (int i = 0; i < 100; i++) {
            Logger.log(this, Logger.LogType.ERROR, "test 1");
            Logger.info(this, "test 1");
            Logger.warning(this, "test 1");
            Logger.error(this, "test 1");
        }
        Logger.setDebugOff();

        File testlocFile = new File(testloc);

        asyncWaitForFileCreation(testloc);
        assertTrue(testlocFile.exists());

        int count = 0;
        File file = new File(testloc);
        FileReader fileReader = new FileReader(file);
        BufferedReader reader = new BufferedReader(fileReader);
        while (reader.readLine() != null) {
            ++count;
        }
        reader.close();

        assertEquals(10, count);
    }
    @Test
    public void test_getters() throws ClassCastException {
        assertTrue(Logger.getLogDir() instanceof String);
        assertTrue(Logger.getLogLength() == Logger.getLogLength());
    }

    private void asyncWaitForFileCreation(String testloc) throws Exception {
        with().pollDelay(ONE_HUNDRED_MILLISECONDS)
                .and().with().pollInterval(TWO_HUNDRED_MILLISECONDS)
                .and().with().timeout(ONE_MINUTE)
                .await("file creation")
                .until(fileIsCreatedOnDisk(testloc), equalTo(true));
    }

    private void asyncWaitForFileRemoval(String testloc) throws Exception {
        with().pollDelay(ONE_HUNDRED_MILLISECONDS)
                .and().with().pollInterval(TWO_HUNDRED_MILLISECONDS)
                .and().with().timeout(ONE_MINUTE)
                .await("file removal")
                .until(fileIsRemovedFromDisk(testloc), equalTo(true));
    }

    private Callable<Boolean> fileIsCreatedOnDisk(final String filename) {
        return () -> {
            File file = new File(filename);
            return file.exists();
        };
    }

    private Callable<Boolean> fileIsRemovedFromDisk(final String filename) {
        return () -> {
            File file = new File(filename);
            return !file.exists();
        };
    }
}

Travis 作业日志

:test
Download https://jcenter.bintray.com/org/jacoco/org.jacoco.agent/0.7.7.201606060606/org.jacoco.agent-0.7.7.201606060606.pom
Download https://jcenter.bintray.com/org/jacoco/org.jacoco.build/0.7.7.201606060606/org.jacoco.build-0.7.7.201606060606.pom
Download https://jcenter.bintray.com/org/jacoco/org.jacoco.agent/0.7.7.201606060606/org.jacoco.agent-0.7.7.201606060606.jar
tetris.LoggerTest > test_logcreate FAILED
    java.util.concurrent.TimeoutException at LoggerTest.java:36
tetris.LoggerTest > test_capLog FAILED
    java.util.concurrent.TimeoutException at LoggerTest.java:94
47 tests completed, 2 failed
:test FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':test'.

Answer 1

在您的第一个测试用例中，您没有给记录器线程足够的时间来创建文件。这可能适用于某些操作系统，但 Travis CI 很慢。建议:创建一个方法，以一定的间隔(例如 100 毫秒)轮询条件(在本例中，文件存在)一段时间(至少五秒)。

private static boolean pollForCondition(Callable<Boolean> condition) {
  while (/* ... */) {
    if (condition.call().booleanValue()) {
      return true;
    }
    // ...
  }
  return false;
}

应该在所有测试用例中使用此方法(在 assertTrue() 中)。

此外，考虑到您的测试用例的执行顺序未确定(从 Java 6 或 7 开始，AFAIK)。在下一个测试用例开始之前，您是否在某处删除了创建的文件？