@Override
    public void rotate(IndexSet indexSet) {
        indexRotator.rotate(indexSet, this::shouldRotate);
    }
@Test
    public void shouldRotateThrowsNPEIfIndexSetConfigIsNull() throws Exception {
        when(indexSet.getConfig()).thenReturn(null);
        when(indexSet.getNewestIndex()).thenReturn(IGNORED);

        expectedException.expect(NullPointerException.class);
        expectedException.expectMessage("Index set configuration must not be null");

        rotationStrategy.rotate(indexSet);
    }