ci: make some slow tests run only under NOKOGIRI_GC

and speed a few other tests up. suite drops from ~22s to ~6s on my dev
machine (with GC_LEVEL=minor).

test/helper.rb

@@ -20,7 +20,7 @@
 
 require 'minitest/autorun'
 require 'minitest/reporters'
-NOKOGIRI_MINITEST_REPORTERS_OPTIONS = { color: true, slow_count: 5, detailed_skip: false }
+NOKOGIRI_MINITEST_REPORTERS_OPTIONS = { color: true, slow_count: 10, detailed_skip: false }
 NOKOGIRI_MINITEST_REPORTERS_OPTIONS[:fast_fail] = true if ENV["NOKOGIRI_TEST_FAIL_FAST"]
 puts "Minitest::Reporters options: #{NOKOGIRI_MINITEST_REPORTERS_OPTIONS}"
 Minitest::Reporters.use!(Minitest::Reporters::DefaultReporter.new(NOKOGIRI_MINITEST_REPORTERS_OPTIONS))

test/xml/test_node.rb

@@ -1197,9 +1197,11 @@ def test_set_node_lang
         end
 
         def test_text_node_robustness_gh1426
+          skip("only run if NOKOGIRI_GC is set") unless ENV['NOKOGIRI_GC']
           skip("No need to test libxml-ruby workarounds on JRuby") if Nokogiri.jruby?
           # notably, the original bug report was about libxml-ruby interactions
           # this test should blow up under valgrind if we regress on libxml-ruby workarounds
+          # side note: this was fixed in libxml-ruby 2.9.0 by https://github.com/xml4r/libxml-ruby/pull/119
           message = "<section><h2>BOOM!</h2></section>"
           10_000.times do
             node = Nokogiri::HTML::DocumentFragment.parse(message).at_css("h2")

test/xml/test_node_set.rb

@@ -889,13 +889,18 @@ def awesome!; end
               <?xml version="1.0" encoding="UTF-8"?>
               <container></container>
             EOF
+
+            # proc that returns Nodes but allows the Documents to be GCed
             scope = lambda do
               Nokogiri::XML::Document.parse(xml).css("container") + Nokogiri::XML::Document.parse(xml).css("container")
             end
-            stress_memory_while do
-              node_set = scope.call
-              node_set.to_s
-            end
+            node_set = scope.call
+
+            # kick off major GC
+            GC.start
+
+            # see if everything's still there
+            node_set.to_s
           end
 
           it "should handle this case just fine" do

test/xml/test_reader.rb

@@ -61,14 +61,14 @@ def test_reader_blocking
           end
           rd.close
         end
-        sleep(1)              # sleep for one second to make sure the reader will actually block for input
+        sleep(0.1) # sleep to make sure the reader will actually block for input
         begin
           wr.puts "<foo>"
           wr.puts "<bar/>" * 10000
           wr.flush
         rescue Errno::EPIPE
         end
-        res = t.join(5)    # wait 5 seconds for the thread to finish
+        res = t.join(1) # give the thread a moment to finish
         wr.close
         refute_nil node_out, "Didn't read any nodes, exclude the trivial case"
         refute_nil res, "Reader blocks trying to read the entire stream"

test/xml/test_reader_encoding.rb

@@ -121,6 +121,7 @@ def test_name
       end
 
       def test_value_lookup_segfault
+        skip("only run if NOKOGIRI_GC is set") unless ENV['NOKOGIRI_GC']
         skip("JRuby doesn't do GC.") if Nokogiri.jruby?
         stress_memory_while do
           while node = @reader.read