Flutter: Test that a specific exception is thrown

问题

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));

回答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:

回答2:

In case anyone wants to test with an async function like I had to do all you need to do is add async keyword in the expect, bearing in mind that the lookupOrderDetails is an async function:

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

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

It still uses Gunter's answer which is very good!

回答3:

First import correct package 'package:matcher/matcher.dart';

expect(() => yourOperation.yourMethod(),
      throwsA(const TypeMatcher<YourException>()));

来源：https://stackoverflow.com/questions/54241396/flutter-test-that-a-specific-exception-is-thrown

标签

dart

Flutter

flutter-test