`test_linear_performance_percent_gt` is flaky results with Ruby 3.1

[hsbt]

From ruby/ruby#11172 (comment)

I found test_linear_performance_percent_gt is failed sometimes with Ruby 3.1 and REXML 3.3.2.

• https://github.com/ruby/actions/actions/workflows/snapshot-ruby_3_1.yml
• https://github.com/ruby/actions/actions/runs/10022301424/job/27701976765#step:17:180

I'm not sure we should relax that limit for Ruby 3.1. Could you give the idea for that?

[kou]

It seems that Ruby 3.1 uses tool/lib/core_assertions.rb not test-unit-ruby-core:

https://github.com/ruby/actions/actions/runs/10022301424/job/27701976765#step:17:185

  /home/runner/work/actions/actions/snapshot-ruby_3_1/tool/lib/core_assertions.rb:757:in `block (2 levels) in assert_linear_performance'

Can we use test-unit-ruby-core with Ruby 3.1 too?

[kou]

test-unit-ruby-core doesn't have the https://github.com/ruby/ruby/blob/ruby_3_1/tool/lib/core_assertions.rb#L757 assertion.
If we can use test-unit-ruby-core (only) for bundled gem tests, we will be able to fix this problem.

[hsbt]

I merged assert_linear_performance changes at ruby/ruby#11581. It may resolved this flaky result.