4 Per the issue, the latest version of flutter has updated to Dart 2.1 and recommends libraries update dart sdk upper bound to <3.0.0. See: https://github.com/flutter/flutter/wiki/Changelog. Also, updating to Dart 2.1 causes issues with the test.dart library version you specified, so I removed that bound.
4 Per the issue, the latest version of flutter has updated to Dart 2.1 and recommends libraries update dart sdk upper bound to <3.0.0. See: https://github.com/flutter/flutter/wiki/Changelog. Also, updating to Dart 2.1 causes issues with the test.dart library version you specified, so I removed that bound.