### Question:
ConfigValueMapStringView extends AbstractMap<String, ConfigValue> { @Override public boolean containsKey(final Object key) { return delegate.containsKey(key); } ConfigValueMapStringView(final Map<String, String> delegate, final String configSourceName,
            final int configSourceOrdinal); @Override int size(); @Override boolean isEmpty(); @Override boolean containsKey(final Object key); @Override boolean containsValue(final Object value); @Override ConfigValue get(final Object key); @Override Set<String> keySet(); @Override Set<Map.Entry<String, ConfigValue>> entrySet(); @Override Collection<ConfigValue> values();  }### Answer:
@Test public void containsKey() { final Map<String, ConfigValue> map = sampleMap(); assertTrue(map.containsKey("my.prop")); assertTrue(map.containsKey("my.null")); }