Week 5 - simple test cases

DijkstraTest.java

package com.github.fbiville.coursera.algorithmics_stanford.week5;

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.util.Lists.newArrayList;

import org.testng.annotations.Test;

import com.google.common.collect.Lists;

public class DijkstraTest {

    private Graph graph;

    @Test
    public void should_compute_shortest_path_for_single_vertex() {
        given_a_single_vertex_graph();

        ShortestPaths paths = new Dijkstra(graph).computeShortestPaths(vertex("1"));

        assertThat(paths.contains(vertex("1"))).isTrue();
        assertThat(paths.cost(vertex("1"))).isZero();
    }

    @Test
    public void should_compute_shortest_path_for_single_edge() {
        given_a_single_edge_graph("1", "2", 42);

        ShortestPaths paths = new Dijkstra(graph).computeShortestPaths(vertex("1"));

        assertThat(paths.contains(vertex("1"), vertex("2"))).isTrue();
        assertThat(paths.cost(vertex("2"))).isEqualTo(42);
    }

    @Test
    public void should_compute_shortest_path_for_two_different_edges() {
        given_a_graph(edge("1", "2", 23), edge("1", "3", 24));

        ShortestPaths paths = new Dijkstra(graph).computeShortestPaths(vertex("1"));

        assertThat(paths.contains(vertex("1"), vertex("2"), vertex("3"))).isTrue();
        assertThat(paths.cost(vertex("2"))).isEqualTo(23);
        assertThat(paths.cost(vertex("3"))).isEqualTo(24);
    }

    @Test
    public void should_compute_shortest_path_for_two_connected_edges() {
        given_a_graph(edge("1", "2", 23), edge("2", "3", 24));

        ShortestPaths paths = new Dijkstra(graph).computeShortestPaths(vertex("1"));

        assertThat(paths.contains(vertex("1"), vertex("2"), vertex("3"))).isTrue();
        assertThat(paths.cost(vertex("2"))).isEqualTo(23);
        assertThat(paths.cost(vertex("3"))).isEqualTo(47);
    }

    @Test
    public void should_compute_shortest_path_for_redundant_edges() {
        given_a_graph(edge("1", "2", 23), edge("1", "3", 24), edge("2", "3", 2));

        ShortestPaths paths = new Dijkstra(graph).computeShortestPaths(vertex("1"));

        assertThat(paths.contains(vertex("1"), vertex("2"), vertex("3"))).isTrue();
        assertThat(paths.cost(vertex("2"))).isEqualTo(23);
        assertThat(paths.cost(vertex("3"))).isEqualTo(24);
    }

    private void given_a_single_vertex_graph() {
        graph = new Graph(Lists.<WeightedEdge>newArrayList());
    }

    private void given_a_single_edge_graph(String label, String otherLabel, long weight) {
        graph = new Graph(newArrayList(new WeightedEdge(vertex(label), vertex(otherLabel), weight)));
    }

    private void given_a_graph(WeightedEdge... edges) {
        graph = new Graph(newArrayList(edges));
    }

    private WeightedEdge edge(String label1, String label2, int weight) {
        return new WeightedEdge(vertex(label1), vertex(label2), weight);
    }

    private Vertex vertex(String label) {
        return new Vertex(label);
    }
}