### Question:
Snapshot { public List<LibId> getChangedLibraries(Snapshot oldSnapshot) { if (oldSnapshot == null) { oldSnapshot = idManager.getInitialSnapshot(); } if (idManager != oldSnapshot.idManager) { throw new IllegalArgumentException(); } List<LibId> changed = null; if (oldSnapshot.libBackups != libBackups) { int numLibs = Math.max(oldSnapshot.libBackups.size(), libBackups.size()); for (int i = 0; i < numLibs; i++) { LibraryBackup oldBackup = oldSnapshot.getLib(i); LibraryBackup newBackup = getLib(i); if (oldBackup == newBackup) { continue; } if (changed == null) { changed = new ArrayList<LibId>(); } changed.add(idManager.getLibId(i)); } } if (changed == null) { changed = Collections.emptyList(); } return changed; } private  Snapshot(IdManager idManager, int snapshotId, Tool tool,
            ImmutableArrayList<CellTree> cellTrees,
            ImmutableArrayList<CellBackup> cellBackups,
            int[] cellGroups, CellId[] groupMainSchematics,
            ImmutableArrayList<LibraryBackup> libBackups,
            Environment environment);  Snapshot(IdManager idManager); Snapshot with(Tool tool, Environment environment, CellBackup[] cellBackupsArray, LibraryBackup[] libBackupsArray); Snapshot with(Tool tool, Environment environment, CellTree[] cellTreesArray, LibraryBackup[] libBackupsArray); Snapshot with(Tool tool, Environment environment); Snapshot withRenamedIds(IdMapper idMapper, CellId fromGroup, String toGroup); List<LibId> getChangedLibraries(Snapshot oldSnapshot); List<CellId> getChangedCells(Snapshot oldSnapshot); Collection<CellId> getCellsDownTop(); CellTree getCellTree(CellId cellId); CellBackup getCell(CellId cellId); CellRevision getCellRevision(CellId cellId); CellTree getCellTree(int cellIndex); CellBackup getCell(int cellIndex); CellRevision getCellRevision(int cellIndex); static CellName makeCellGroupName(Collection<CellName> cellNames); EquivalentSchematicExports getEquivExports(CellId top); ERectangle getCellBounds(CellId cellId); ERectangle getCellBounds(int cellIndex); int getCellGroupIndex(CellId cellId); boolean cellGroupsProbablyChanged(Snapshot that); CellId getMainSchematics(CellId cellId); TechPool getTechPool(); Technology getTech(TechId techId); Artwork getArtwork(); Generic getGeneric(); Schematics getSchematics(); Map<Setting, Object> getSettings(); LibraryBackup getLib(LibId libId); void writeDiffs(IdWriter writer, Snapshot oldSnapshot); static Snapshot readSnapshot(IdReader reader, Snapshot oldSnapshot); void check(); final IdManager idManager; final int snapshotId; final Tool tool; final ImmutableArrayList<CellTree> cellTrees; final ImmutableArrayList<CellBackup> cellBackups; final ImmutableArrayList<LibraryBackup> libBackups; final Environment environment; final TechPool techPool; }### Answer:
@Test public void testGetChangedLibraries() { System.out.println("getChangedLibraries"); Snapshot oldSnapshot = initialSnapshot; Snapshot instance = initialSnapshot; List<LibId> expResult = Collections.emptyList(); List<LibId> result = instance.getChangedLibraries(oldSnapshot); assertEquals(expResult, result); }