### Question:
ConstrettoBuilder { public static ConstrettoBuilder fromExistingConfiguration(final ConstrettoConfiguration constrettoConfiguration, final ConfigurationContextResolver configurationContextResolver) { Objects.requireNonNull(constrettoConfiguration, "The \"constrettoConfiguration\" argument can not be null"); Objects.requireNonNull(configurationContextResolver, "The \"configurationContextResolver\" argument can not be null"); return new ConstrettoBuilder(configurationContextResolver, false).addExistingConfiguration(constrettoConfiguration); } @Deprecated  ConstrettoBuilder(); @Deprecated  ConstrettoBuilder(boolean enableSystemProps);  ConstrettoBuilder(ConfigurationContextResolver configurationContextResolver, boolean enableSystemProps); private  ConstrettoBuilder(List<ConfigurationStore> configurationStores, List<String> tags, boolean enableSystemProps); static ConstrettoBuilder withSystemProperties(final ConfigurationContextResolver contextResolver); static ConstrettoBuilder withSystemProperties(); static ConstrettoBuilder empty(); static ConstrettoBuilder empty(final ConfigurationContextResolver configurationContextResolver); static ConstrettoBuilder fromExistingConfiguration(final ConstrettoConfiguration constrettoConfiguration, final ConfigurationContextResolver configurationContextResolver); static ConstrettoBuilder fromExistingConfiguration(final ConstrettoConfiguration constrettoConfiguration); ConstrettoConfiguration getConfiguration(); ConstrettoBuilder addCurrentTag(String tag); ConstrettoBuilder addConfigurationStore(ConfigurationStore configurationStore); ConstrettoBuilder addExistingConfiguration(final ConstrettoConfiguration constrettoConfiguration); PropertiesStoreBuilder createPropertiesStore(); EncryptedPropertiesStoreBuilder createEncryptedPropertiesStore(String passwordProperty); IniFileConfigurationStoreBuilder createIniFileConfigurationStore(); JsonStoreBuilder createJsonConfigurationStore(); ConstrettoBuilder createSystemPropertiesStore(); ObjectConfigurationStoreBuilder createObjectConfigurationStore(); WrappedLdapConfigurationStoreBuilder createLdapConfigurationStore(final DirContext dirContext); YamlStoreBuilder createYamlConfigurationStore(); static final String OVERRIDES; }### Answer:
@Test public void testFromExistingConfiguration() throws Exception { final ConstrettoConfiguration preExistingConfiguration = ConstrettoBuilder.empty(STATIC_CONTEXT_RESOLVER) .createObjectConfigurationStore() .addObject(new UntaggedConfig()) .addObject(new TaggedConfig()) .done().getConfiguration(); assertEquals(TaggedConfig.TAGGED_VALUE, preExistingConfiguration.evaluateToString("value")); final ConstrettoConfiguration configuration = ConstrettoBuilder.fromExistingConfiguration(preExistingConfiguration, PredefinedConfigurationContextResolver.empty()).getConfiguration(); assertEquals(TaggedConfig.TAGGED_VALUE, configuration.evaluateToString("value")); }