### Question:
AbstractInstanceManager { public V registerSingle(final K parent, final V instance) { return this.singletons.put(parent, instance); }  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 registerSingle() { this.instanceManager.registerSingle(PARENT, ACTUAL_1); assertThat(this.instanceManager.getSingle(PARENT).get()).isEqualTo(ACTUAL_1); }