### Question:
ChainAction extends Action { @Override public ValidationResult validate(ActionInstance actionInstance) { return isValidGbpChain(actionInstance.getParameterValue()); }  void setResolvedSymmetricChains(List<String> resolvedSymmetricChains); @Override ActionDefinitionId getId(); @Override ActionDefinition getActionDef(); @Override List<ActionBuilder> updateAction(List<ActionBuilder> actions, Map<String, Object> params, Integer order,
                                            NetworkElements netElements, OfWriter ofWriter,
                                            OfContext ctx, Direction direction); @Override ValidationResult validate(ActionInstance actionInstance); static ServiceFunctionPath getSfcPath(SfcName chainName); @Override List<SupportedParameterValues> getSupportedParameterValues();  }### Answer:
@Test public void testIsValid_ParameterValueNull() { ActionInstance actionInstance = mock(ActionInstance.class); Assert.assertFalse(chainAction.validate(actionInstance).isValid()); }