Flutter: Test that a specific exception is thrown

Question

in short, throwsA(anything) does not suffice for me while unit testing in dart. How to I test for a specific error message or type?

Here is the error I would like to catch:

class MyCustErr implements Exception {
  String term;

  String errMsg() => 'You have already added a container with the id 
  $term. Duplicates are not allowed';

  MyCustErr({this.term});
}

here is the current assertion that passes, but would like to check for the error type above:

expect(() => operations.lookupOrderDetails(), throwsA(anything));

This is what I want to do:

expect(() => operations.lookupOrderDetails(), throwsA(MyCustErr));

Answer 1

This should do what you want:

expect(() => operations.lookupOrderDetails(), throwsA(const TypeMatcher<MyCustErr>()));

expect(() => operations.lookupOrderDetails(), isInstanceOf<MyCustErr>());

if you just want to check for exception check this answer: