### Question:
AbstractInstanceManager { public List<V> getAll(final K parent) { final List<V> all = this.getMultiples(parent); this.getSingle(parent).peek(all::add); return all; }  V registerSingle(final K parent, final V instance); V registerMultiple(
        final K parent,
        final Selector selector,
        final V instance
    ); Option<V> getMultiple(final K parent, final Selector selector); List<V> getAll(final K parent); List<V> getMultiples(final K parent); Option<V> getSingle(final K parent);  }### Answer:
@Test public void getAll() { this.instanceManager.registerSingle(PARENT, ACTUAL_1); this.instanceManager.registerSingle(PARENT, ACTUAL_2); this.instanceManager.registerMultiple(PARENT, SEL_1, ACTUAL_1); this.instanceManager.registerMultiple(PARENT, SEL_2, ACTUAL_2); final List<String> all = this.instanceManager.getAll(PARENT); assertThat(all).containsExactlyInAnyOrder( ACTUAL_1, ACTUAL_2, ACTUAL_2 ); }