@Test
  public void addANodeAndSampleableGoesUp() {
    double oldValue = sampleable.getValue();

    createNode(db);

    assertThat(sampleable.getValue(), greaterThan(oldValue));
  }
 @Test
 public void emptyDbHasZeroNodesInUse() {
   assertThat(sampleable.getValue(), is(0d));
 }