@Test
  public void testTouch() throws Exception {
    DefaultDiskStorage storage = getStorageSupplier(1).get();
    final long startTime = 0;

    final String resourceId1 = "resource1";
    final byte[] value1 = new byte[100];
    final File file1 = writeFileToStorage(storage, resourceId1, value1);
    assertTrue(Math.abs(file1.lastModified() - startTime) <= 500);

    final long time2 = startTime + 10000;
    when(mClock.now()).thenReturn(time2);
    final String resourceId2 = "resource2";
    final byte[] value2 = new byte[100];
    final File file2 = writeFileToStorage(storage, resourceId2, value2);
    assertTrue(Math.abs(file1.lastModified() - startTime) <= 500);
    assertTrue(Math.abs(file2.lastModified() - time2) <= 500);

    final long time3 = time2 + 10000;
    when(mClock.now()).thenReturn(time3);
    storage.touch(resourceId1, null);
    assertTrue(Math.abs(file1.lastModified() - time3) <= 500);
    assertTrue(Math.abs(file2.lastModified() - time2) <= 500);
  }
Inserts 3 files with different dates. Check what files are there. Uses an iterator to remove
the one in the middle. Check that later.

@throws Exception
imagepipeline-base/src/test/java/com/facebook/cache/disk/DefaultDiskStorageTest.java