utils/misc/src/test/java/org/onlab/graph/KShortestPathsSearchTest.java

package org.onlab.graph;

import com.google.common.collect.Lists;
import org.junit.Before;
import org.junit.Test;

import java.util.Iterator;
import java.util.List;
import java.util.Set;

import static com.google.common.collect.ImmutableSet.of;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

/**
 * Class for test KshortestPathsSearch.
 */
public class KShortestPathsSearchTest<V extends Vertex, E extends Edge<V>> extends GraphTest {
    private KShortestPathsSearch<TestVertex, TestEdge> kShortestPathsSearch = new KShortestPathsSearch<>();
    private GraphPathSearch.Result<TestVertex, TestEdge> result;

    @Before
    public void setUp() {
        graph = new AdjacencyListsGraph<>(vertexes(), edges());
    }
    @Test
    public void noPath() {
        graph = new AdjacencyListsGraph<>(of(A, B, C, D),
                                          of(new TestEdge(A, B, 1),
                                             new TestEdge(B, A, 1),
                                             new TestEdge(C, D, 1),
                                             new TestEdge(D, C, 1)));
        KShortestPathsSearch<TestVertex, TestEdge> kShortestPathsSearch = new KShortestPathsSearch<>();
        GraphPathSearch.Result<TestVertex, TestEdge> result = kShortestPathsSearch.search(graph, A, D, weight, 1);
        Set<Path<TestVertex, TestEdge>> resultPathSet = result.paths();
        assertTrue("There should not be any paths.", resultPathSet.isEmpty());
    }

    @Test
    public void testSinglePath() {
        //Tests that there is only a single path possible between A and B
        graph = new AdjacencyListsGraph<>(vertexes(), edges());
        this.result = kShortestPathsSearch.search(graph, A, B, weight, 2);
        Iterator<Path<TestVertex, TestEdge>> itr = result.paths().iterator();
        assertEquals("incorrect paths count", 1, result.paths().size());
        List<TestEdge> correctEdgeList = Lists.newArrayList();
        correctEdgeList.add(new TestEdge(A, B, 1));
        assertTrue("That wrong path was returned.",
                   edgeListsAreEqual(correctEdgeList, result.paths().iterator().next().edges()));
    }

    @Test
    public void testTwoPath() {
        //Tests that there are only two paths between A and C and that they are returned in the correct order
        result = kShortestPathsSearch.search(graph, A, C, weight, 3);
        assertTrue("There are an unexpected number of paths.", result.paths().size() == 2);
        Iterator<Path<TestVertex, TestEdge>> edgeListIterator = result.paths().iterator();
        List<TestEdge> correctEdgeList = Lists.newArrayList();
        correctEdgeList.add(new TestEdge(A, B, 1));
        correctEdgeList.add(new TestEdge(B, C, 1));
        assertTrue("The first path from A to C was incorrect.",
                   edgeListsAreEqual(edgeListIterator.next().edges(), correctEdgeList));
        correctEdgeList.clear();
        correctEdgeList.add(new TestEdge(A, C, 3));
        assertTrue("The second path from A to C was incorrect.",
                   edgeListsAreEqual(edgeListIterator.next().edges(), correctEdgeList));
    }

    @Test
    public void testFourPath() {
        //Tests that there are only four paths between A and E and that they are returned in the correct order
        //Also tests the special case where some correct solutions are equal
        result = kShortestPathsSearch.search(graph, A, E, weight, 5);
        assertTrue("There are an unexpected number of paths.", result.paths().size() == 4);
        Iterator<Path<TestVertex, TestEdge>> edgeListIterator = result.paths().iterator();
        List<TestEdge> correctEdgeList = Lists.newArrayList();
        correctEdgeList.add(new TestEdge(A, B, 1));
        correctEdgeList.add(new TestEdge(B, C, 1));
        correctEdgeList.add(new TestEdge(C, E, 1));
        assertTrue("The first path from A to E was incorrect.",
                   edgeListsAreEqual(edgeListIterator.next().edges(), correctEdgeList));
        correctEdgeList.clear();
        //There are two paths of equal length that should hold positions two and three
        List<TestEdge> alternateCorrectEdgeList = Lists.newArrayList();
        correctEdgeList.add(new TestEdge(A, C, 3));
        correctEdgeList.add(new TestEdge(C, E, 1));
        alternateCorrectEdgeList.add(new TestEdge(A, B, 1));
        alternateCorrectEdgeList.add(new TestEdge(B, D, 2));
        alternateCorrectEdgeList.add(new TestEdge(D, E, 1));
        List<TestEdge> candidateOne = edgeListIterator.next().edges();
        List<TestEdge> candidateTwo = edgeListIterator.next().edges();
        if (candidateOne.size() == 2) {
            assertTrue("The second path from A to E was incorrect.",
                       edgeListsAreEqual(candidateOne, correctEdgeList));
            assertTrue("The third path from A to E was incorrect.",
                       edgeListsAreEqual(candidateTwo, alternateCorrectEdgeList));
        } else {
            assertTrue("The second path from A to E was incorrect.",
                       edgeListsAreEqual(candidateOne, alternateCorrectEdgeList));
            assertTrue("The third path from A to E was incorrect.",
                       edgeListsAreEqual(candidateTwo, correctEdgeList));
        }
        correctEdgeList.clear();
        correctEdgeList.add(new TestEdge(A, B, 1));
        correctEdgeList.add(new TestEdge(B, E, 4));
        assertTrue("The fourth path rom A to E was incorrect",
                   edgeListsAreEqual(edgeListIterator.next().edges(), correctEdgeList));

    }

    @Test
    public void testPathsFromSink() {
        //H is a sink in this topology, insure there are no paths from it to any other location
        for (TestVertex vertex : vertexes()) {
            assertTrue("There should be no paths from vertex H to any other node.",
                       kShortestPathsSearch.search(graph, H, vertex, weight, 1).paths().size() == 0);
        }
    }

    @Test
    public void testLimitPathSetSize() {
        //Checks to make sure that no more than K paths are returned
        result = kShortestPathsSearch.search(graph, A, E, weight, 3);
        assertTrue("There are an unexpected number of paths.", result.paths().size() == 3);
        result = kShortestPathsSearch.search(graph, A, G, weight, 1);
        assertTrue("There are an unexpected number of paths.", result.paths().size() == 1);
    }

    private boolean edgeListsAreEqual(List<TestEdge> edgeListOne, List<TestEdge> edgeListTwo) {
        if (edgeListOne.size() != edgeListTwo.size()) {
            return false;
        }
        TestEdge edgeOne;
        TestEdge edgeTwo;
        for (int i = 0; i < edgeListOne.size(); i++) {
            edgeOne = edgeListOne.get(i);
            edgeTwo = edgeListTwo.get(i);
            if (!edgeOne.equals(edgeTwo)) {
                return false;
            }
        }
        return true;
    }
}