exclude name must be Regexp or Symbol

fdf0f8d814/tool/lib/test/unit.rb (L1273-L1290)

test/excludes/TestThread.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: false
 exclude(/_stack_size$/, 'often too expensive')
 if /freebsd13/ =~ RUBY_PLATFORM
-  exclude('test_signal_at_join', 'gets stuck somewhere')
+  exclude(:test_signal_at_join, 'gets stuck somewhere')
 end