dispose method

@override void dispose()

Close stream controllers and restore TaskChainBuilder.enqueueCallback.

Must be called in tearDown to prevent:

• Stream subscription leaks.
• Test contamination via the static TaskChainBuilder.enqueueCallback.

Implementation

@override
void dispose() {
  // C-02 fix: restore the original enqueueCallback so subsequent tests
  // (or production code) are not affected by this fake.
  TaskChainBuilder.enqueueCallback = _savedEnqueueCallback;
  _eventsController.close();
  _progressController.close();
}