CompositeExceptionTest.java

/**
 * Copyright 2014 Netflix, Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package rx.exceptions;

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

import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.junit.Test;

public class CompositeExceptionTest {

    private final Throwable ex1 = new Throwable("Ex1");
    private final Throwable ex2 = new Throwable("Ex2", ex1);
    private final Throwable ex3 = new Throwable("Ex3", ex2);

    public CompositeExceptionTest() {
    }

    private CompositeException getNewCompositeExceptionWithEx123() {
        List<Throwable> throwables = new ArrayList<Throwable>();
        throwables.add(ex1);
        throwables.add(ex2);
        throwables.add(ex3);
        return new CompositeException(throwables);
    }

    @Test(timeout = 1000)
    public void testMultipleWithSameCause() {
        Throwable rootCause = new Throwable("RootCause");
        Throwable e1 = new Throwable("1", rootCause);
        Throwable e2 = new Throwable("2", rootCause);
        Throwable e3 = new Throwable("3", rootCause);
        CompositeException ce = new CompositeException("3 failures with same root cause", Arrays.asList(e1, e2, e3));

        System.err.println("----------------------------- print composite stacktrace");
        ce.printStackTrace();
        assertEquals(3, ce.getExceptions().size());
        
        assertNoCircularReferences(ce);
        assertNotNull(getRootCause(ce));
        System.err.println("----------------------------- print cause stacktrace");
        ce.getCause().printStackTrace();
    }

    @Test(timeout = 1000)
    public void testCompositeExceptionFromParentThenChild() {
        CompositeException cex = new CompositeException(Arrays.asList(ex1, ex2));
        
        System.err.println("----------------------------- print composite stacktrace");
        cex.printStackTrace();
        assertEquals(2, cex.getExceptions().size());
        
        assertNoCircularReferences(cex);
        assertNotNull(getRootCause(cex));
        
        System.err.println("----------------------------- print cause stacktrace");
        cex.getCause().printStackTrace();
    }

    @Test(timeout = 1000)
    public void testCompositeExceptionFromChildThenParent() {
        CompositeException cex = new CompositeException(Arrays.asList(ex2, ex1));
        
        System.err.println("----------------------------- print composite stacktrace");
        cex.printStackTrace();
        assertEquals(2, cex.getExceptions().size());
        
        assertNoCircularReferences(cex);
        assertNotNull(getRootCause(cex));
        
        System.err.println("----------------------------- print cause stacktrace");
        cex.getCause().printStackTrace();
    }

    @Test(timeout = 1000)
    public void testCompositeExceptionFromChildAndComposite() {
        CompositeException cex = new CompositeException(Arrays.asList(ex1, getNewCompositeExceptionWithEx123()));
        
        System.err.println("----------------------------- print composite stacktrace");
        cex.printStackTrace();
        assertEquals(3, cex.getExceptions().size());
        
        assertNoCircularReferences(cex);
        assertNotNull(getRootCause(cex));

        System.err.println("----------------------------- print cause stacktrace");
        cex.getCause().printStackTrace();
    }

    @Test(timeout = 1000)
    public void testCompositeExceptionFromCompositeAndChild() {
        CompositeException cex = new CompositeException(Arrays.asList(getNewCompositeExceptionWithEx123(), ex1));
        
        System.err.println("----------------------------- print composite stacktrace");
        cex.printStackTrace();
        assertEquals(3, cex.getExceptions().size());
        
        assertNoCircularReferences(cex);
        assertNotNull(getRootCause(cex));

        System.err.println("----------------------------- print cause stacktrace");
        cex.getCause().printStackTrace();
    }

    @Test(timeout = 1000)
    public void testCompositeExceptionFromTwoDuplicateComposites() {
        List<Throwable> exs = new ArrayList<Throwable>();
        exs.add(getNewCompositeExceptionWithEx123());
        exs.add(getNewCompositeExceptionWithEx123());
        CompositeException cex = new CompositeException(exs);
        
        System.err.println("----------------------------- print composite stacktrace");
        cex.printStackTrace();
        assertEquals(3, cex.getExceptions().size());
        
        assertNoCircularReferences(cex);
        assertNotNull(getRootCause(cex));

        System.err.println("----------------------------- print cause stacktrace");
        cex.getCause().printStackTrace();
    }

    /**
     * This hijacks the Throwable.printStackTrace() output and puts it in a string, where we can look for
     * "CIRCULAR REFERENCE" (a String added by Throwable.printEnclosedStackTrace)
     */
    private static void assertNoCircularReferences(Throwable ex) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        PrintStream printStream = new PrintStream(baos);
        ex.printStackTrace(printStream);
        assertFalse(baos.toString().contains("CIRCULAR REFERENCE"));
    }

    private static Throwable getRootCause(Throwable ex) {
        Throwable root = ex.getCause();
        if (root == null) {
            return null;
        } else {
            while(true) {
                if (root.getCause() == null) {
                    return root;
                } else {
                    root = root.getCause();
                }
            }
        }
    }
}