This test has been failing sporadically for some time when indy is enabled:

  1) Failure:
TestArray#test_insert [/home/runner/work/jruby/jruby/test/mri/ruby/test_array.rb:2601]:
TypeError expected but nothing was raised.

This is a strange one, because the TypeError should be raised inside Array#insert and I don't see how indy could change that behavior.