### Question:
CacheManagerFactory { public static CacheManager getCacheManager(final String cacheName) { notNull(cacheName, "cacheName cannot be null!"); return new CacheManager(CACHE_MAP.computeIfAbsent(cacheName, k -> new ConcurrentHashMap<>())); }  static CacheManager getCacheManager(final String cacheName);  }### Answer:
@Test(expectedExceptions = IllegalArgumentException.class) public void testGetCacheThrowsExceptionIfTheCacheNameIsNull() { underTest.getCacheManager(null); }
@Test public void testGetCacheReturnsACacheManagerInstance() { final CacheManager actual = underTest.getCacheManager(CACHE_NAME); assertThat(actual).isNotNull(); }