### Question:
ConfigSourceMap extends AbstractMap<String, String> implements Map<String, String>, Serializable { public String get(final Object key) { return key instanceof String ? delegate.getValue((String) key) : null; } ConfigSourceMap(final ConfigSource delegate); int size(); boolean isEmpty(); boolean containsKey(final Object key); String get(final Object key); Set<String> keySet(); Collection<String> values(); Set<Entry<String, String>> entrySet(); void forEach(final BiConsumer<? super String, ? super String> action);  }### Answer:
@Test public void testGet() { final ConfigSourceMap csm = new ConfigSourceMap(MANY_CONF_SRC); assertEquals("bar", csm.get("test")); assertNull(csm.get("null-valued-key")); assertNull(csm.get("nope")); }