ExceptionChecker.java

/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2011, Open Source Geospatial Foundation (OSGeo)
 *
 *    This file is hereby placed into the Public Domain. This means anyone is
 *    free to do whatever they wish with this file. Use it well and enjoy!
 */
package org.geotools;

import static org.junit.Assert.fail;

/**
 * This is a little helper class to provide more rigorous checking of exceptions.
 * It allows you to set an expectation about exactly what the error message should say, 
 * instead of just checking the type.
 * 
 * Just because you happened to get an IOException, for instance, it doesn't mean it
 * was the IOException you thought you should get - it could have been for a different
 * reason, which means your test wouldn't actually be verifying what you intended.
 *
 */
public final class ExceptionChecker {
	/**
	 * Assert that the provided exception's message is the same as the one provided.
	 * If the messages don't match then junit's fail(...) method is called,
	 * if they do match then the original exception is re-thrown to be handled by the
	 * calling code - usually by a Test(expected = ***Exception.class) annotation.
	 * @param exception
	 * 		The exception you want to check.
	 * @param expectedMessage
	 * 		The message you expect the exception to include.
	 * @throws Exception
	 * 		Throws the original exception back if the message DOES match. This
	 * 		means you still need to have the annotation: Test(expected = ***Exception.class)
	 */
    public static void assertExceptionMessage(Exception exception, String expectedMessage)
            throws Exception {
        String actualMessage = exception.getMessage();
        if (actualMessage.compareTo(expectedMessage) != 0) {
            fail(String.format("Expected %s to say: '%s' but got: '%s'", exception.getClass()
                    .getSimpleName(), expectedMessage, actualMessage));
        }

        throw exception;
    }
}