Move to file option for test groups

[FMorschel]

I have this project and it was first structured with all new subclasses being created on the same file but I made a choice to separate them all into specific files (this pattern could also start to happen with sealed classes and part files in the future).

Now, the tests for the project were following the same structure as the /lib/src so all tests for one class were written on the same file inside another group for it. And now I have the grinding work to move all classes to their specific files mainly being solved by Move top-level to file (except a few bugs with exports with currently open issues for them).

But to move every group is a bit grinding still and I'd like to ask for a similar feature to move top-level groups that don't refer to anything outside their scope into new files with the overhead of adding the new void main() { ... } and imports.

[dart-github-bot]

Summary: User requests a "Move group to file" refactoring feature in Dart's test runner, mirroring the existing "Move top-level to file" functionality for improved test organization. This would automate moving test groups to separate files.

[bwilkerson]

The best proposal (that I can think of that's consistent with our general design for features like this) would be to implement an 'extract function' refactoring that would work like 'extract method' but in a top-level (or local?) function. That would allow you to extract the group to a new function, (manually) remove the invocation, and move the top-level function to a different file, where you could rename it to main.