Our text input integration testing doesn't cover IME-based input such as for Chinese, Japanese, and Korean. At the moment, this is covered by non-platform-specific unit tests.

We should include tests that:

1. Set the input method to an IME-based input method.
2. Send a sequence of key events such that are handled by the IME.
3. Verify the text editing contents, in particular, the composing region.

A few things to test:

• Ensure arrow cursor movement is restricted to the composing region when composing (in Chinese/Japanese)
• Test composing in Flutter, then switching to a non-Flutter textfield, composing there, and switching back to flutter. See [macOS] Fix IME input issue caused on FlutterTextInputPlugin dealloc. engine#31879.
• Ensure backspace handling is correct while composing.
• Ensure Escape key handling is correct.
• Verify keyboard navigation of candidates menu is possible (and not captured by Flutter).