DistanceAxiomsTests.java

/**
 * Copyright (c) 2012, 2014 Obeo.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Obeo - initial API and implementation
 */
package org.eclipse.emf.compare.tests.fullcomparison;

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

import com.google.common.collect.Lists;

import org.eclipse.emf.compare.CompareFactory;
import org.eclipse.emf.compare.Comparison;
import org.eclipse.emf.compare.match.eobject.EditionDistance;
import org.eclipse.emf.compare.match.eobject.ProximityEObjectMatcher.DistanceFunction;
import org.eclipse.emf.compare.tests.suite.AllTests;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.emf.ecore.EcorePackage;
import org.junit.Assume;
import org.junit.Before;
import org.junit.experimental.theories.DataPoints;
import org.junit.experimental.theories.Theories;
import org.junit.experimental.theories.Theory;
import org.junit.runner.RunWith;

/**
 * This is a brute force tests using JUnit4 theories to check a distance function really is a distance
 * function in the mathematical sense. It checks all the axioms using the Ecore.ecore model as an input model.
 * <b>It is going to fail</b> with the EditionDistance implementation, so far I could not implement one which
 * is conform to the triangular inequality axiom preventing us to use any kind of clever sorting. That said it
 * looks like we don't really need it so far, looks like we are going fast enough. I'd like to keep this test
 * around anyway as its neet and it might be of use at some point.
 * 
 * @author <a href="mailto:cedric.brun@obeo.fr">Cedric Brun</a>
 */
@SuppressWarnings("nls")
@RunWith(Theories.class)
public class DistanceAxiomsTests {

	private DistanceFunction meter;

	private Comparison comparison;

	@Before
	public void setUp() throws Exception {
		AllTests.fillEMFRegistries();
		this.comparison = CompareFactory.eINSTANCE.createComparison();
		this.meter = new EditionDistance();
	}

	@DataPoints
	public static EObject[] allEcore = createFingerPrintsFromModel(EcorePackage.eINSTANCE);

	@Theory
	public void symetry(EObject a, EObject b) {
		Assume.assumeTrue(a.eClass() == b.eClass());
		double aTob = meter.distance(comparison, a, b);
		double bToa = meter.distance(comparison, b, a);
		assertEquals(aTob, bToa, 0.01);
	}

	private static EObject[] createFingerPrintsFromModel(EObject einstance) {
		return Lists.newArrayList(einstance.eAllContents()).toArray(new EObject[0]);
	}

	@Theory
	public void separation(EObject a) {
		assertEquals(0, meter.distance(comparison, a, a), 0.01);
	}

	@Theory
	public void triangularInequality(EObject x, EObject y, EObject z) {
		Assume.assumeTrue(x.eClass() == y.eClass() && x.eClass() == z.eClass());
		double xToz = meter.distance(comparison, x, z);
		double xToy = meter.distance(comparison, x, y);
		double yToz = meter.distance(comparison, y, z);
		assertTrue(
				"Triangular inequality (x-z <= x-y + y-z ) failed (" + xToz + "<=" + xToy + " + " + yToz
						+ ")for \nx:" + x.toString() + "\n|y:" + y.toString() + "\n|z:" + z.toString(),
				xToz <= xToy + yToz);
	}

}