com.mediamiser.test.Log4j1ErrorAppender Maven / Gradle / Ivy

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A set of utilities to aid in difficult unit-testing.

There is a newer version: 1.0.3

// Copyright (c) 2013-2014 MediaMiser Ltd. All rights reserved.
package com.mediamiser.test;

import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.Level;
import org.apache.log4j.spi.LoggingEvent;

/**
 * A log4j1 extension that will throw an {@code java.lang.AssertionError} if a
 * {@code Level.ERROR} logging statement is propagated to an slf4j logger.
 * 
 * 

 * 

 * This is used to detect whether an error condition is met during the course of
 * unit tests. If a test causes production code to log an error, it will fail
 * the test by throwing an {@code java.lang.AssertionError}. For code coverage
 * reasons, tests still need to ensure that when an error condition occurs that
 * a {@code Level.ERROR} logging statement is propagated to an slf4j logger;
 * this can be accomplished using {@link com.mediamiser.test.LogTester}.
 * 
 * 

 * 

 * To use this appender in your test suite, add it to the root logger before any
 * tests run, e.g., before your test suite is run:
 * 
 * 

 * 

 * 
 *  * public class MyTestSuite {
 * 
 * 	@BeforeClass
 * 	public static void failTestWhenItLogsAnError() {
 * 		Logger.getRootLogger().addAppender(new Log4j1ErrorAppender());
 * 	}
 * 
 * }
 * 
 * 
 * @author Chris Fournier 
 */
public class Log4j1ErrorAppender extends AppenderSkeleton {

	@Override
	public void close() {
		// Do nothing
	}

	@Override
	public boolean requiresLayout() {
		return false;
	}

	@Override
	protected void append(final LoggingEvent event) {
		// If an error was logged, throw an assertion so that the test that
		// caused the error will fail
		if (event.getLevel() == Level.ERROR) {
			throw new AssertionError("Test logged at the error level: " + event.getMessage());
		}
	}

}