flutter test したところ、以下のように Too many open files というエラーがでた。


...

05:05 +2049 ~15 -364: loading /Applications/flutter/packages/flutter/test/widgets/editable_text_cursor_test.dart [E]
  Failed to load "/Applications/flutter/packages/flutter/test/widgets/editable_text_cursor_test.dart":
  Too many open files
    Command: /Applications/flutter/bin/cache/artifacts/engine/darwin-x64/flutter_tester --disable-observatory --enable-checked-mode --verify-entry-points --enable-software-rendering --skia-deterministic-rendering --enable-dart-profiling --non-interactive --use-test-fonts --packages=/Applications/flutter/packages/flutter/.packages /var/folders/56/pjxy3nxx16v_bcn0jrkx4d6c0000gn/T/flutter_test_listener.P9AoAx/listener.dart.dill
05:15 +2075 ~15 -364: Some tests failed.

ulimitで一時的に上限を増やしましょう。

ulimit -S -n 2048

See: https://flutter.dev/docs/testing/debugging