Fix some warnings in the test suite #590

Job	Run time
Ruby memcheck	49s
ruby-versions / Generate Ruby versions	2s
ubuntu-22.04 2.7	1m 10s
ubuntu-22.04 3.0	32s
ubuntu-22.04 3.1	40s
ubuntu-22.04 3.2	31s
ubuntu-22.04 3.3	33s
ubuntu-22.04 head	1m 45s
ubuntu-22.04 jruby	1m 9s
ubuntu-22.04 jruby-head	1m 28s
macos-13 2.7	3m 13s
macos-13 3.0	35s
macos-13 3.1	48s
macos-13 3.2	49s
macos-13 3.3	40s
macos-13 head	37s
macos-13 jruby	1m 26s
macos-13 jruby-head	2m 25s
macos-14 2.7	1m 2s
macos-14 3.0	25s
macos-14 3.1	27s
macos-14 3.2	20s
macos-14 3.3	25s
macos-14 head	17s
macos-14 jruby	43s
macos-14 jruby-head	45s
windows-latest 2.7	3m 32s
windows-latest 3.0	2m 0s
windows-latest 3.1	1m 55s
windows-latest 3.2	2m 25s
windows-latest 3.3	5m 37s
windows-latest head	1m 54s
windows-latest mswin	1m 20s
ubuntu-latest jruby-9.4	1m 26s
macos-latest truffleruby-head	37s
ubuntu-latest truffleruby-head	2m 6s
	46m 28s

Provide feedback