diff --git a/test/objspace/test_objspace.rb b/test/objspace/test_objspace.rb
index 3f4a58e98d..b54a438132 100644
--- a/test/objspace/test_objspace.rb
+++ b/test/objspace/test_objspace.rb
@@ -244,39 +244,38 @@ class TestObjSpace < Test::Unit::TestCase
 
   def test_trace_object_allocations_start_stop_clear
     ObjectSpace.trace_object_allocations_clear # clear object_table to get rid of erroneous detection for obj3
-    GC.disable # suppress potential object reuse. see [Bug #11271]
-    begin
-      ObjectSpace.trace_object_allocations_start
+    EnvUtil.without_gc do # suppress potential object reuse. see [Bug #11271]
       begin
         ObjectSpace.trace_object_allocations_start
         begin
           ObjectSpace.trace_object_allocations_start
-          obj0 = Object.new
+          begin
+            ObjectSpace.trace_object_allocations_start
+            obj0 = Object.new
+          ensure
+            ObjectSpace.trace_object_allocations_stop
+            obj1 = Object.new
+          end
         ensure
           ObjectSpace.trace_object_allocations_stop
-          obj1 = Object.new
+          obj2 = Object.new
         end
       ensure
         ObjectSpace.trace_object_allocations_stop
-        obj2 = Object.new
+        obj3 = Object.new
       end
-    ensure
-      ObjectSpace.trace_object_allocations_stop
-      obj3 = Object.new
+
+      assert_equal(__FILE__, ObjectSpace.allocation_sourcefile(obj0))
+      assert_equal(__FILE__, ObjectSpace.allocation_sourcefile(obj1))
+      assert_equal(__FILE__, ObjectSpace.allocation_sourcefile(obj2))
+      assert_equal(nil     , ObjectSpace.allocation_sourcefile(obj3)) # after tracing
+
+      ObjectSpace.trace_object_allocations_clear
+      assert_equal(nil, ObjectSpace.allocation_sourcefile(obj0))
+      assert_equal(nil, ObjectSpace.allocation_sourcefile(obj1))
+      assert_equal(nil, ObjectSpace.allocation_sourcefile(obj2))
+      assert_equal(nil, ObjectSpace.allocation_sourcefile(obj3))
     end
-
-    assert_equal(__FILE__, ObjectSpace.allocation_sourcefile(obj0))
-    assert_equal(__FILE__, ObjectSpace.allocation_sourcefile(obj1))
-    assert_equal(__FILE__, ObjectSpace.allocation_sourcefile(obj2))
-    assert_equal(nil     , ObjectSpace.allocation_sourcefile(obj3)) # after tracing
-
-    ObjectSpace.trace_object_allocations_clear
-    assert_equal(nil, ObjectSpace.allocation_sourcefile(obj0))
-    assert_equal(nil, ObjectSpace.allocation_sourcefile(obj1))
-    assert_equal(nil, ObjectSpace.allocation_sourcefile(obj2))
-    assert_equal(nil, ObjectSpace.allocation_sourcefile(obj3))
-  ensure
-    GC.enable
   end
 
   def test_trace_object_allocations_gc_stress
diff --git a/test/ruby/test_gc.rb b/test/ruby/test_gc.rb
index de64cbd36d..9a9796dc55 100644
--- a/test/ruby/test_gc.rb
+++ b/test/ruby/test_gc.rb
@@ -40,16 +40,16 @@ class TestGc < Test::Unit::TestCase
   end
 
   def test_enable_disable
-    GC.enable
-    assert_equal(false, GC.enable)
-    assert_equal(false, GC.disable)
-    assert_equal(true, GC.disable)
-    assert_equal(true, GC.disable)
-    assert_nil(GC.start)
-    assert_equal(true, GC.enable)
-    assert_equal(false, GC.enable)
-  ensure
-    GC.enable
+    EnvUtil.without_gc do
+      GC.enable
+      assert_equal(false, GC.enable)
+      assert_equal(false, GC.disable)
+      assert_equal(true, GC.disable)
+      assert_equal(true, GC.disable)
+      assert_nil(GC.start)
+      assert_equal(true, GC.enable)
+      assert_equal(false, GC.enable)
+    end
   end
 
   def test_gc_config_full_mark_by_default
@@ -227,12 +227,9 @@ class TestGc < Test::Unit::TestCase
     GC.stat(stat)
 
     GC::INTERNAL_CONSTANTS[:SIZE_POOL_COUNT].times do |i|
-      begin
-        reenable_gc = !GC.disable
+      EnvUtil.without_gc do
         GC.stat_heap(i, stat_heap)
         GC.stat(stat)
-      ensure
-        GC.enable if reenable_gc
       end
 
       assert_equal (GC::INTERNAL_CONSTANTS[:BASE_SLOT_SIZE] + GC::INTERNAL_CONSTANTS[:RVALUE_OVERHEAD]) * (2**i), stat_heap[:slot_size]
@@ -768,23 +765,17 @@ class TestGc < Test::Unit::TestCase
   end
 
   def test_gc_disabled_start
-    begin
-      disabled = GC.disable
+    EnvUtil.without_gc do
       c = GC.count
       GC.start
       assert_equal 1, GC.count - c
-    ensure
-      GC.enable unless disabled
     end
 
-    begin
-      disabled = GC.disable
+    EnvUtil.without_gc do
       c = GC.count
       GC.start(immediate_mark: false, immediate_sweep: false)
       10_000.times { Object.new }
       assert_equal 1, GC.count - c
-    ensure
-      GC.enable unless disabled
     end
   end
 
@@ -859,28 +850,26 @@ class TestGc < Test::Unit::TestCase
   end
 
   def test_old_to_young_reference
-    original_gc_disabled = GC.disable
+    EnvUtil.without_gc do
+      require "objspace"
 
-    require "objspace"
+      old_obj = Object.new
+      4.times { GC.start }
 
-    old_obj = Object.new
-    4.times { GC.start }
+      assert_include ObjectSpace.dump(old_obj), '"old":true'
 
-    assert_include ObjectSpace.dump(old_obj), '"old":true'
+      young_obj = Object.new
+      old_obj.instance_variable_set(:@test, young_obj)
 
-    young_obj = Object.new
-    old_obj.instance_variable_set(:@test, young_obj)
+      # Not immediately promoted to old generation
+      3.times do
+        assert_not_include ObjectSpace.dump(young_obj), '"old":true'
+        GC.start
+      end
 
-    # Not immediately promoted to old generation
-    3.times do
-      assert_not_include ObjectSpace.dump(young_obj), '"old":true'
+      # Takes 4 GC to promote to old generation
       GC.start
+      assert_include ObjectSpace.dump(young_obj), '"old":true'
     end
-
-    # Takes 4 GC to promote to old generation
-    GC.start
-    assert_include ObjectSpace.dump(young_obj), '"old":true'
-  ensure
-    GC.enable if !original_gc_disabled
   end
 end
diff --git a/test/ruby/test_objectspace.rb b/test/ruby/test_objectspace.rb
index 0364cf7093..beb66da7e2 100644
--- a/test/ruby/test_objectspace.rb
+++ b/test/ruby/test_objectspace.rb
@@ -191,30 +191,29 @@ End
   end
 
   def test_finalizer_thread_raise
-    GC.disable
-    fzer = proc do |id|
-      sleep 0.2
-    end
-    2.times do
-      o = Object.new
-      ObjectSpace.define_finalizer(o, fzer)
-    end
-
-    my_error = Class.new(RuntimeError)
-    begin
-      main_th = Thread.current
-      Thread.new do
-        sleep 0.1
-        main_th.raise(my_error)
+    EnvUtil.without_gc do
+      fzer = proc do |id|
+        sleep 0.2
+      end
+      2.times do
+        o = Object.new
+        ObjectSpace.define_finalizer(o, fzer)
+      end
+
+      my_error = Class.new(RuntimeError)
+      begin
+        main_th = Thread.current
+        Thread.new do
+          sleep 0.1
+          main_th.raise(my_error)
+        end
+        GC.start
+        puts "After GC"
+        sleep(10)
+        assert(false)
+      rescue my_error
       end
-      GC.start
-      puts "After GC"
-      sleep(10)
-      assert(false)
-    rescue my_error
     end
-  ensure
-    GC.enable
   end
 
   def test_each_object
diff --git a/test/ruby/test_sleep.rb b/test/ruby/test_sleep.rb
index 61002b8b18..991b73ebd5 100644
--- a/test/ruby/test_sleep.rb
+++ b/test/ruby/test_sleep.rb
@@ -4,14 +4,13 @@ require 'etc'
 
 class TestSleep < Test::Unit::TestCase
   def test_sleep_5sec
-    GC.disable
-    start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
-    sleep 5
-    slept = Process.clock_gettime(Process::CLOCK_MONOTONIC) - start
-    bottom = 5.0
-    assert_operator(slept, :>=, bottom)
-    assert_operator(slept, :<=, 6.0, "[ruby-core:18015]: longer than expected")
-  ensure
-    GC.enable
+    EnvUtil.without_gc do
+      start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      sleep 5
+      slept = Process.clock_gettime(Process::CLOCK_MONOTONIC) - start
+      bottom = 5.0
+      assert_operator(slept, :>=, bottom)
+      assert_operator(slept, :<=, 6.0, "[ruby-core:18015]: longer than expected")
+    end
   end
 end
diff --git a/test/ruby/test_string_memory.rb b/test/ruby/test_string_memory.rb
index e264dd5705..a93a3bd54a 100644
--- a/test/ruby/test_string_memory.rb
+++ b/test/ruby/test_string_memory.rb
@@ -6,32 +6,31 @@ class TestStringMemory < Test::Unit::TestCase
   def capture_allocations(klass)
     allocations = []
 
-    GC.start
-    GC.disable
-    generation = GC.count
+    EnvUtil.without_gc do
+      GC.start
+      generation = GC.count
 
-    ObjectSpace.trace_object_allocations do
-      yield
+      ObjectSpace.trace_object_allocations do
+        yield
 
-      ObjectSpace.each_object(klass) do |instance|
-        allocations << instance if ObjectSpace.allocation_generation(instance) == generation
+        ObjectSpace.each_object(klass) do |instance|
+          allocations << instance if ObjectSpace.allocation_generation(instance) == generation
+        end
+      end
+
+      return allocations.map do |instance|
+        [
+          ObjectSpace.allocation_sourcefile(instance),
+          ObjectSpace.allocation_sourceline(instance),
+          instance.class,
+          instance,
+        ]
+      end.select do |path,|
+        # drop strings not created in this file
+        # (the parallel testing framework may create strings in a separate thread)
+        path == __FILE__
       end
     end
-
-    return allocations.map do |instance|
-      [
-        ObjectSpace.allocation_sourcefile(instance),
-        ObjectSpace.allocation_sourceline(instance),
-        instance.class,
-        instance,
-      ]
-    end.select do |path,|
-      # drop strings not created in this file
-      # (the parallel testing framework may create strings in a separate thread)
-      path == __FILE__
-    end
-  ensure
-    GC.enable
   end
 
   def test_byteslice_prefix