### Question:
ZookeeperConfiguration implements GovernanceConfiguration { @Override public boolean deleteConfig(String key) { return deleteConfig(null, key); }  @Override void setUrl(URL url); @Override URL getUrl(); @Override void init(); @Override String setConfig(String key, String value); @Override String getConfig(String key); @Override boolean deleteConfig(String key); @Override String setConfig(String group, String key, String value); @Override String getConfig(String group, String key); @Override boolean deleteConfig(String group, String key); @Override String getPath(String key); @Override String getPath(String group, String key);  }### Answer:
@Test public void testDeleteConfig() { assertEquals(false, configuration.deleteConfig("not_exist_key")); configuration.setConfig("test_delete", "test_value"); assertEquals("test_value", configuration.getConfig("test_delete")); configuration.deleteConfig("test_delete"); assertEquals(null, configuration.getConfig("test_delete")); assertEquals(false, configuration.deleteConfig("test_group", "not_exist_key")); configuration.setConfig("test_group", "test_delete", "test_value"); assertEquals("test_value", configuration.getConfig("test_group", "test_delete")); configuration.deleteConfig("test_group", "test_delete"); assertEquals(null, configuration.getConfig("test_group", "test_delete")); try { configuration.deleteConfig(null); fail("should throw IllegalArgumentException for null key"); } catch (IllegalArgumentException e) { } }