isMockValidator

isMockValidator is useful when we need to access the callback which was set via registerOnValidatorChange on a mock object which has implemented Validator or AsyncValidator, and to call __simulateValidatorChange to trigger it. It verifies whether an instance respects MockValidator interface.

We need it when we get an error like:

Property '__simulateValidatorChange' does not exist on type <class>

const instance = ngMocks.findInstance(MyValidatorDirective);
// instance.simulateValidatorChange(); // does not work.
if (isMockValidator(instance)) {
  // now works
  instance.__simulateValidatorChange();
}