void testGetUpstreamProjects() throws CycleDetectedException, DuplicateProjectException {
        ProjectDependencyGraph graph = threeProjectsDependingOnASingle();
        final List<MavenProject> downstreamProjects = graph.getUpstreamProjects(depender1, true);
        assertEquals(aProject, downstreamProjects.get(0));
    }

    private ProjectDependencyGraph threeProjectsDependingOnASingle()

            Set<MavenProject> projectsSet = new HashSet<>(projects);

            for (MavenProject project : projects) {
                if (makeUpstream) {
                    projectsSet.addAll(graph.getUpstreamProjects(project, true));
                }
                if (makeDownstream) {
                    projectsSet.addAll(graph.getDownstreamProjects(project, true));
                }
            }

        final MavenSession session = createMavenSession(pom);
        session.setProjectDependencyGraph(new ProjectDependencyGraph() {
            @Override
            public List<MavenProject> getUpstreamProjects(MavenProject project, boolean transitive) {
                return Collections.emptyList();
            }

            @Override
            public List<MavenProject> getAllProjects() {