AbstractCache implements IDataCache<T> { @Override public long getFreeSpace() { return maxCacheSize - getCurrentCacheSize(); } AbstractCache(S entries, IDataStorage<T> cachedStorage, long maxCacheSize,
      Predicate<T> cachingRule); @Override long getMaxCacheSize(); @Override boolean setMaxCacheSize(long maxCacheSize); @Override long getCurrentCacheSize(); @Override long getFreeSpace(); @Override boolean hasStorageFor(long size); @Override void cacheData(T data); @Override void uncacheData(T data); @Override boolean dataIsCachable(T data); @Override boolean dataIsInCache(long id); @Override void clearCache(); @Override boolean dataExists(long id); @Override T loadData(long id); @Override boolean saveData(T data); @Override boolean dataIsStorable(T data); @Override boolean deleteData(T data);  }
@Test public void testGetFreeSpace() { AbstractCacheWrapper uut = new AbstractCacheWrapper(entries, storageAll, IDataCache.STD_MAX_CACHE_SIZE, predicate -> true); assertEquals(IDataCache.STD_MAX_CACHE_SIZE, uut.getFreeSpace()); uut.cacheData(c0); assertEquals(IDataCache.STD_MAX_CACHE_SIZE - c0.getByteSize(), uut.getFreeSpace()); uut.cacheData(c1); assertEquals(IDataCache.STD_MAX_CACHE_SIZE - (c0.getByteSize() + c1.getByteSize()), uut.getFreeSpace()); }