@Test
 public void diskLruCacheAsyncGet_whenEmpty_shouldReturnNull() throws Exception {
   CacheService.initialize(context);
   CacheService.getFromDiskCacheAsync(key1, diskCacheGetListener);
   semaphore.acquire();
   assertThat(getKey).isEqualTo(key1);
   assertThat(getBytes).isNull();
 }
 @Test
 public void diskLruCacheAsyncGet_whenPopulated_shouldReturnValue() throws Exception {
   CacheService.initialize(context);
   assertCachesAreEmpty();
   CacheService.putToDiskCache(key1, data1.getBytes());
   CacheService.getFromDiskCacheAsync(key1, diskCacheGetListener);
   semaphore.acquire();
   assertThat(getKey).isEqualTo(key1);
   assertThat(getBytes).isEqualTo(data1.getBytes());
 }