test/ruby (*no_hidden_garbage): disable GC and skip if multi-threaded

Any single object allocation can reduce object count, and
object counts are global, so multi-threading leads to unpredictable
results.

See also similar commits: r60699 and r62608

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63885 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_sprintf.rb

@@ -524,12 +524,17 @@ class TestSprintf < Test::Unit::TestCase
   end
 
   def test_no_hidden_garbage
+    skip unless Thread.list.size == 1
+
     fmt = [4, 2, 2].map { |x| "%0#{x}d" }.join('-') # defeats optimization
     ObjectSpace.count_objects(res = {}) # creates strings on first call
+    GC.disable
     before = ObjectSpace.count_objects(res)[:T_STRING]
     val = sprintf(fmt, 1970, 1, 1)
     after = ObjectSpace.count_objects(res)[:T_STRING]
     assert_equal before + 1, after, 'only new string is the created one'
     assert_equal '1970-01-01', val
+  ensure
+    GC.enable
   end
 end

test/ruby/test_time.rb

@@ -1109,11 +1109,14 @@ class TestTime < Test::Unit::TestCase
     fmt = %w(Y m d).map { |x| "%#{x}" }.join('-') # defeats optimization
     t = Time.at(0).getutc
     ObjectSpace.count_objects(res = {}) # creates strings on first call
+    GC.disable
     before = ObjectSpace.count_objects(res)[:T_STRING]
     val = t.strftime(fmt)
     after = ObjectSpace.count_objects(res)[:T_STRING]
     assert_equal before + 1, after, 'only new string is the created one'
     assert_equal '1970-01-01', val
+  ensure
+    GC.enable
   end
 
   def test_num_exact_error