### Question:
InstalledExtensionDocumentTree { public Set<DocumentReference> getNestedCustomizedExtensionPages(EntityReference rootReference) { return getNestedExtensionPages(rootReference).stream().filter(this::isCustomizedExtensionPage) .collect(Collectors.toSet()); }  Set<DocumentReference> getChildren(EntityReference parentReference); boolean isExtensionPage(DocumentReference documentReference); boolean isCustomizedExtensionPage(DocumentReference documentReference); Set<DocumentReference> getNestedExtensionPages(EntityReference rootReference); Set<DocumentReference> getNestedCustomizedExtensionPages(EntityReference rootReference);  }### Answer:
@Test public void getNestedCustomizedExtensionPages() { this.tree.setCustomizedExtensionPage(this.alice, true); this.tree.setCustomizedExtensionPage(this.bob, false); this.tree.setCustomizedExtensionPage(new DocumentReference(this.denis, Locale.FRENCH), true); assertEquals(Collections.singleton(this.alice), this.tree.getNestedCustomizedExtensionPages(this.alice.getWikiReference())); assertEquals(Collections.singleton(this.alice), this.tree.getNestedCustomizedExtensionPages(this.path)); assertEquals(Collections.singleton(this.denis), this.tree.getNestedCustomizedExtensionPages(this.carol.getWikiReference())); assertEquals(Collections.emptySet(), this.tree.getNestedCustomizedExtensionPages(this.carol)); assertEquals(Collections.singleton(this.denis), this.tree.getNestedCustomizedExtensionPages(this.users)); assertEquals(Collections.emptySet(), this.tree.getNestedCustomizedExtensionPages(new WikiReference("test"))); assertEquals(Collections.emptySet(), this.tree.getNestedCustomizedExtensionPages(this.bob)); assertEquals(Collections.emptySet(), this.tree.getNestedCustomizedExtensionPages(this.path.getLastSpaceReference())); assertEquals(Collections.emptySet(), this.tree.getNestedCustomizedExtensionPages(new DocumentReference("bar", "Path", "WebHome"))); assertEquals(Collections.emptySet(), this.tree.getNestedCustomizedExtensionPages(new DocumentReference(this.path, Locale.FRENCH))); }