PropertyProviderImpl implements PropertyProvider { @Override public boolean hasProperty(String propertyName) { return propertyProviders.containsKey(propertyName); }  @Override boolean hasProperty(String propertyName); @SuppressWarnings("unchecked") @Override Object getProperty(Object object, String propertyName); @Override void register(String property, Function<?, Object> function);  }
@Test void hasProperty() { provider.register(PROPERTY, key -> VALUE); assertTrue(provider.hasProperty(PROPERTY)); assertFalse(provider.hasProperty("does not exist")); }