assertEquals(expected2, actual2);

        Graph graph3 = new Graph();
        graph3.addVertex("a");
        graph3.addVertex("b");
        graph3.addVertex("c");
        graph3.addVertex("d");
        graph3.addVertex("e");
        graph3.addVertex("f");
        addEdge(graph3, "a", "b");
        addEdge(graph3, "b", "c");
        addEdge(graph3, "b", "d");

         *   v1<
         *       v3-v4
         *
         */
        v1 = graph.addVertex(new ArtifactMetadata("g", "a1", "1.0"));
        graph.setEntry(v1);
        v2 = graph.addVertex(new ArtifactMetadata("g", "a2", "1.0"));
        v3 = graph.addVertex(new ArtifactMetadata("g", "a3", "1.0"));
        v4 = graph.addVertex(new ArtifactMetadata("g", "a4", "1.0"));

        // v1-->v2

                                    ? null
                                    : edge.getTarget().getMd().getError());
                    MetadataGraphVertex newV = res.addVertex(newMd);
                    MetadataGraphVertex sourceV = res.addVertex(edge.getSource().getMd());

                    res.addEdge(sourceV, newV, edge);
                }
            }

         *
         */
        graph = new MetadataGraph(4, 3);
        v1 = graph.addVertex(new ArtifactMetadata("g", "a1", "1.0"));
        graph.setEntry(v1);
        v2 = graph.addVertex(new ArtifactMetadata("g", "a2", "1.0"));
        v3 = graph.addVertex(new ArtifactMetadata("g", "a3", "1.0"));
        v4 = graph.addVertex(new ArtifactMetadata("g", "a4", "1.0"));

        // v1-->v2

    public Vertex getVertex(String id) {
        return vertices.get(id);
    }

    public Collection<Vertex> getVertices() {
        return vertices.values();
    }

    Vertex addVertex(String label) {
        return vertices.computeIfAbsent(label, Vertex::new);
    }

    void addEdge(Vertex from, Vertex to) throws CycleDetectedException {
        from.children.add(to);
        to.parents.add(from);

    public Vertex getVertex(String id) {
        return vertices.get(id);
    }

    public Collection<Vertex> getVertices() {
        return vertices.values();
    }

    Vertex addVertex(String label) {
        return vertices.computeIfAbsent(label, Vertex::new);
    }

    void addEdge(Vertex from, Vertex to) throws CycleDetectedException {
        from.children.add(to);
        to.parents.add(from);

            Map<String, Vertex> vertices = vertexMap.computeIfAbsent(projectKey, k -> new HashMap<>(2, 1));

            vertices.put(project.getVersion(), graph.addVertex(projectId));
        }

        for (Vertex projectVertex : graph.getVertices()) {
            String projectId = projectVertex.getLabel();

            MavenProject project = projectMap.get(projectId);

                return gv;
            }
        }

        return null;
    }
    // ------------------------------------------------------------------------
    public MetadataGraphVertex addVertex(ArtifactMetadata md) {
        if (md == null) {
            return null;
        }

        checkVertices();

        MetadataGraphVertex v = findVertex(md);
        if (v != null) {

public synchronized class DAG implements Cloneable, java.io.Serializable { private java.util.Map vertexMap; private java.util.List vertexList; public void DAG(); public java.util.List getVerticies(); public java.util.Set getLabels(); public Vertex addVertex(String); public void addEdge(String, String) throws CycleDetectedExcepti; public void addEdge(Vertex, Vertex) throws CycleDetectedExcepti; public void removeEdge(String, String); public void removeEdge(Vertex, Vertex); public Vertex getVertex(String);...

public synchronized class DAG implements Cloneable, java.io.Serializable { private java.util.Map vertexMap; private java.util.List vertexList; public void DAG(); public java.util.List getVerticies(); public java.util.Set getLabels(); public Vertex addVertex(String); public void addEdge(String, String) throws CycleDetectedExcepti; public void addEdge(Vertex, Vertex) throws CycleDetectedExcepti; public void removeEdge(String, String); public void removeEdge(Vertex, Vertex); public Vertex getVertex(String);...