@Test
public void findNodes() {

    Set<Node> nodes = index.findNodes("x:green");
    assertThat(nodes).hasSize(1);
    assertThat(nodes).contains(v1);
    nodes = index.findNodes("x:yellow");
    assertThat(nodes).hasSize(3);
    assertThat(nodes).contains(v3, v4, v5);
}