Use case

The xcode_backend.dart mainly contains a Context class, and the current design is:

// xcode_backend.dart
class Context {
  void func1() { ... }
  void func2() { ... }
}

// xcode_backend_test.dart (unit tests in general.shard)
class TestContext {
  @override
  void func1() { ... }
  @override
  void func2() { ... }
}

For example, one of such functions is runSync:

And it's overwritten here:

This means during unit test, the whole chunk of actual implementation is stubbed out, which defeats the whole purpose of unit tests! For unit test, we should stub out the dependencies of the test subject, not the implementation of test subject itself.

Proposal

Quick fix (short term)

Context can instead introduce a 1-line wrapper function that only contains https://github.com/flutter/flutter/blob/5483fef5384821748cfcc1bfc3157e1f9c0322ea/packages/flutter_tools/bin/xcode_backend.dart#L118C34-L118C41

Then TestContext will just override this wrapper function. Then the rest of the implementation would be run during unit test.

Actual fix

The fact that Context is only inherited by TestContext in tests is an indicator that inheritance isn't the best approach here. We should instead favor composition, by injecting dependencies (e.g. ProcessManager).