First pass of tests

[richardmarshall]

Adds tests for:

• Basic testing of most QuillController logic
• Basic keyboard input validation for QuillEditor
• Android image insertion support in QuillEditor Add support for android keyboard image insertion #1236
• Verification of bug fixes in Prevent operations on stale editor state #1256

Also adds a new importable library flutter_quill_test that can be used by consumers of this package to assist with testing editor behavior in their apps.

[singerdmx]

Validating package... (2.0s)
Package validation found the following error:

• line 2, column 1 of lib/src/test/widget_tester_extension.dart: flutter_test is in the dev_dependencies section of pubspec.yaml. Packages used in lib/ must be declared in the dependencies section.
  ╷
  2 │ import 'package:flutter_test/flutter_test.dart';
  │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[singerdmx]

@richardmarshall This blocks flutter pub publish

[singerdmx]

I am reverting this change.
Please create a new PR once you resolves the publishing issue.

[richardmarshall]

@singerdmx ok, will look into it.

[richardmarshall]

Now aware of the flutter pub publish --dry-run command, will incorporate that into future workflow. Still pretty new to dart and flutter so still learning how all these bits fit together.

@singerdmx I can either add flutter_test to the packages main dependencies list or remove the test helper from lib/. It seems including flutter_test in the dependencies section isn't unheard of as that is what super_editor is doing as well. If you're fine with that change I'll update my branch and submit a new PR.

[singerdmx]

I am unfamiliar with the practice so you can make your own call as long as it doesn't break the publishing