Spying on "echo" breaks bashunit

[RevanProdigalKnight]

Q	A
OS	Linux (Cygwin on Windows)
Shell & version	bash 5.2.21(1)-release
bashunit version	0.33.0

Summary

Spying on or mocking echo or printf causes unit tests to hang

Current behavior

Didn't look until I tried using printf instead of echo but it looks like it's causing bashunit to infinitely spawn processes somewhere.

How to reproduce

function write_data_to_coproc() {
  if [ -z "$COPROC" ]; then
    return 1
  fi
  echo >&"${COPROC[0]}" "set_data: $*"
}

function test_write_data_to_coproc() {
  COPROC=(12 13)
  bashunit::spy echo

  write_data_to_coproc "hello world"
  assert_have_been_called_with echo "set_data: hello world"
}

Probable cause

Unprotected calls to echo/printf instead of using builtin echo/builtin printf

Expected behavior

Unit test completes and bashunit doesn't hang forever.