Thread.sleep(1001);
TestFileUtil.createRandomFile(new File(testCacheFolder, "40"), 40*1024);
assertEquals(4, testCacheFolder.listFiles().length);
cache.clear();
assertEquals(1, testCacheFolder.listFiles().length);
assertFalse(new File(testCacheFolder, "10").exists());
assertFalse(new File(testCacheFolder, "30").exists());
assertFalse(new File(testCacheFolder, "20").exists());