java.lang.AssertionError: test.log size is 25.7MB which is 71.6% more than 15.0MB requested
java.lang.AssertionError: test.log size is 27.7MB which is 176.9% more than 10.0MB requested

package third.party.logback;

import static org.junit.Assert.*;
import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.HashSet;
import java.util.Random;
import java.util.Set;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;
import org.slf4j.LoggerFactory;
import ch.qos.logback.classic.Logger;
import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.encoder.PatternLayoutEncoder;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.core.Appender;
import ch.qos.logback.core.rolling.RollingFileAppender;
import ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP;
import ch.qos.logback.core.rolling.TimeBasedRollingPolicy;

public class TimeRotationTest {
  private static File _tmpDir;
  private Set<File> _filesExpected;

  @BeforeClass
  public static void setupForAll() throws Exception {
    String tmp = System.getProperty("java.io.tmpdir") + "/timedwindowlogbacktest/" + System.currentTimeMillis();
    _tmpDir = new File(tmp);
    _tmpDir.mkdirs();
    assertTrue(_tmpDir + " not created", _tmpDir.isDirectory());
    assertEquals(_tmpDir + " not empty", 0, _tmpDir.list().length);
    for(String p : new String[]{ "java.vendor", "java.version", "os.name", "os.version", "os.arch" } ) {
      System.out.println(p + "=" + System.getProperty(p));
    }
    System.out.println("using " + _tmpDir.getAbsolutePath() + "\n");
  }

  @Before
  public void setup() {
    _filesExpected = new HashSet<File>();
  }

  private void verifyFile(File file, long maxSize) {
    String name = file.getName();
    assertTrue(name + " duplicate", _filesExpected.add(file));
    assertTrue(name + " does not exist", file.canRead());
    assertTrue(name + " size is zero", file.length() > 0);
    float percent = 100f * file.length() / maxSize - 100f;
    String msg = String.format("%s size is %.1fMB which is %.1f%% more than %.1fMB requested",
            name, file.length()/1024f/1024, percent, maxSize/1024f/1024);
    assertTrue(msg, file.length() <= maxSize * 1.1); // give it 10% slack
  }

  private Appender<ILoggingEvent> createAppender(String basename_, String rotated_, long maxFileSize_, int maxFiles_, boolean append_) {
    LoggerContext context = (LoggerContext) LoggerFactory.getILoggerFactory();

    SizeAndTimeBasedFNATP triggeringPolicy = new SizeAndTimeBasedFNATP<ILoggingEvent>();
    triggeringPolicy.setMaxFileSize(String.valueOf(maxFileSize_));

    TimeBasedRollingPolicy<ILoggingEvent> rollingPolicy = new TimeBasedRollingPolicy<ILoggingEvent>();
    rollingPolicy.setContext(context);
    rollingPolicy.setTimeBasedFileNamingAndTriggeringPolicy(triggeringPolicy);
    rollingPolicy.setMaxHistory(maxFiles_ - 1);
    rollingPolicy.setFileNamePattern(rotated_);

    triggeringPolicy.setContext(context);
    triggeringPolicy.setTimeBasedRollingPolicy(rollingPolicy);

    RollingFileAppender<ILoggingEvent> appender = new RollingFileAppender<ILoggingEvent>();
    appender.setFile(basename_);
    appender.setAppend(append_);
    appender.setRollingPolicy(rollingPolicy);
    appender.setTriggeringPolicy(triggeringPolicy);
    rollingPolicy.setParent(appender);
    rollingPolicy.start();
    triggeringPolicy.start();

    PatternLayoutEncoder layout = new PatternLayoutEncoder();
    layout.setPattern("%d{YYYY-MM-dd HH:mm:ss.SSS} [%thread] %level %logger %msg%n");
    layout.setContext(context);
    layout.start();

    appender.setEncoder(layout);
    appender.setContext(context);
    appender.start();
    return appender;
  }

  private void doTest(final String testname, String basenameS, String rotatedS, boolean compress, int maxFiles, long maxSize) throws Exception {
    File testDir = new File(_tmpDir, testname);
    testDir.mkdirs();
    assertEquals(testDir + " not empty", 0, testDir.listFiles().length);

    File basename = new File(testDir, basenameS);
    File rotated  = new File(testDir, rotatedS + (compress ? ".gz" : ""));
    boolean append = false;

    Appender<ILoggingEvent> appender = createAppender(basename.getPath(), rotated.getPath(), maxSize, maxFiles, append);
    org.slf4j.Logger slf4jLog = LoggerFactory.getLogger(testname);  
    Logger logger = (Logger) slf4jLog; 
    logger.addAppender(appender);

    // log some stuff, loads of it
    Random rnd = new Random();
    String msg = "{} During the application {} in the case long-lived application on {} when {} is another random";
    for(int i = 0; i < 200000; ++i) {
      logger.info(msg, System.nanoTime(), new Date(), rnd.nextGaussian());
    }

    for(int i = 0; i < maxFiles - 1; ++i) {
      String file = String.format(resolveFilename(rotated.getPath()), i);
      verifyFile(new File(file), maxSize);
    }

    verifyFile(basename, maxSize);

    Set<File> filesPresent = new HashSet<File>(Arrays.asList(testDir.listFiles()));
    filesPresent.removeAll(_filesExpected);
    assertTrue("unexpected " + filesPresent.size() + " files: " + filesPresent, filesPresent.isEmpty());
  }

  private String resolveFilename(String rotatedPattern_) {
    String dateFormat = null;
    final String DP = "%d{";
    int i = rotatedPattern_.indexOf(DP);
    int j;
    if (i > -1) {
      j = rotatedPattern_.indexOf('}');
      if (j > DP.length() + i) {
        dateFormat = rotatedPattern_.substring(i + DP.length(), j);
      }
    } else {
      dateFormat = "yyyy-MM-dd";
      i = rotatedPattern_.indexOf("%d");
      j = i + 1;
    }
    String s = rotatedPattern_.substring(0, i)
            + new SimpleDateFormat(dateFormat).format(new Date())
            + rotatedPattern_.substring(j + 1);
    return s.replace("%i", "%d");
  }

//  @Test public void testDailyMax3_5MB() throws Exception { doTest("daily_max3_5MB_each", "test.log", "test_%d.log.%i", false, 3, 5 * 1024 * 1024); }
  @Test public void testDailyMax8_5MB() throws Exception { doTest("daily_max8_5MB_each", "test.log", "test_%d.log.%i", false, 8, 5 * 1024 * 1024); }

  @Test public void testDailyMax4_10MB() throws Exception { doTest("daily_max4_10MB_each", "test.log", "test_%d.log.%i", false, 4, 10 * 1024 * 1024); }
//  @Test public void testDailyMax2_10MB() throws Exception { doTest("daily_max2_10MB_each", "test.log", "test_%d.log.%i", false, 2, 10 * 1024 * 1024); }

  @Test public void testOnePerDay_max2_30MB() throws Exception { doTest("one_daily_max2_30MB_each", "test.log", "test_%d.log", false, 2, 30 * 1024 * 1024); }
  @Test public void testOnePerDay_max2_15MB() throws Exception { doTest("one_daily_max2_15MB_each", "test.log", "test_%d.log", false, 2, 15 * 1024 * 1024); }

  @Test public void testCustomPattern() throws Exception { doTest("custom_pattern", "test.log", "test_%d{yyyyMMdd}.log", false, 2, 20 * 1024 * 1024); }

  @Test public void testHourly10MB() throws Exception { doTest("hourly10", "test.log", "test_%d{yyyyMMdd_HH}.log", false, 2, 10 * 1024 * 1024); }
  @Test public void testHourly20MB() throws Exception { doTest("hourly20", "test.log", "test_%d{yyyyMMdd_HH}.log", false, 2, 20 * 1024 * 1024); }
}

java.vendor=Sun Microsystems Inc.
java.version=1.6.0_45
os.name=Windows 7
os.version=6.1
os.arch=amd64