[CI] rescue more errors in teardown & wait_for_server_to_boot methods, RubyGems (#2887)

* test/helpers/integration.rb - updates for exception handling

* test/test_out_of_band_server.rb - fixup teardown

* [CI] tests.yaml - Update RubyGems for Rubies 2.3 - 2.5

.github/workflows/tests.yaml

@@ -85,6 +85,13 @@ jobs:
         continue-on-error: true
         timeout-minutes: 5
 
+      # fixes 'has a bug that prevents `required_ruby_version`'
+      - name: update rubygems for Ruby 2.3 - 2.5
+        if: contains('2.3 2.4 2.5', matrix.ruby)
+        run: gem update --system 3.3.14 --no-document
+        continue-on-error: true
+        timeout-minutes: 5
+
       - name: Compile Puma without SSL support
         if: matrix.no-ssl == ' no SSL'
         shell: bash

test/helpers/integration.rb

@@ -22,6 +22,7 @@ class TestIntegration < Minitest::Test
 
   def setup
     @server = nil
+    @pid = nil
     @ios_to_close = []
     @bind_path    = tmp_path('.sock')
   end
@@ -35,8 +36,12 @@ class TestIntegration < Minitest::Test
 
     if @ios_to_close
       @ios_to_close.each do |io|
-        io.close if io.is_a?(IO) && !io.closed?
-        io = nil
+        begin
+          io.close if io.is_a?(IO) && !io.closed?
+        rescue
+        ensure
+          io = nil
+        end
       end
     end
 
@@ -47,8 +52,12 @@ class TestIntegration < Minitest::Test
 
     # wait until the end for OS buffering?
     if @server
-      @server.close unless @server.closed?
-      @server = nil
+      begin
+        @server.close unless @server.closed?
+      rescue
+      ensure
+        @server = nil
+      end
     end
   end
 
@@ -114,6 +123,8 @@ class TestIntegration < Minitest::Test
   # wait for server to say it booted
   # @server and/or @server.gets may be nil on slow CI systems
   def wait_for_server_to_boot(log: false)
+    sleep 0.05 until @server.is_a?(IO)
+    @server.wait_readable 1
     if log
       puts "Waiting for server to boot..."
       begin
@@ -122,7 +133,6 @@ class TestIntegration < Minitest::Test
       end until line && line.include?('Ctrl-C')
       puts "Server booted!"
     else
-      sleep 0.1 until @server.is_a?(IO)
       true until (@server.gets || '').include?('Ctrl-C')
     end
   end

test/test_out_of_band_server.rb

@@ -15,7 +15,15 @@ class TestOutOfBandServer < Minitest::Test
     @oob_finished.broadcast
     @app_finished.broadcast
     @server.stop(true) if @server
-    @ios.each {|i| i.close unless i.closed?}
+
+    @ios.each do |io|
+      begin
+        io.close if io.is_a?(IO) && !io.closed?
+      rescue
+      ensure
+        io = nil
+      end
+    end
   end
 
   def new_connection