diff --git a/activesupport/test/abstract_unit.rb b/activesupport/test/abstract_unit.rb
index 7ffcae6007..9b88a2dcc1 100644
--- a/activesupport/test/abstract_unit.rb
+++ b/activesupport/test/abstract_unit.rb
@@ -37,4 +37,5 @@ def jruby_skip(message = '')
   skip message if defined?(JRUBY_VERSION)
 end
 
+require 'minitest/mock'
 require 'mocha/setup' # FIXME: stop using mocha
diff --git a/activesupport/test/caching_test.rb b/activesupport/test/caching_test.rb
index dce4e9b051..8e22d4ed2f 100644
--- a/activesupport/test/caching_test.rb
+++ b/activesupport/test/caching_test.rb
@@ -288,8 +288,9 @@ module CacheStoreBehavior
     @cache.write('foo', 'bar', :expires_in => 10)
     @cache.write('fu', 'baz')
     @cache.write('fud', 'biz')
-    Time.stubs(:now).returns(time + 11)
-    assert_equal({"fu" => "baz"}, @cache.read_multi('foo', 'fu'))
+    Time.stub(:now, time + 11) do
+      assert_equal({"fu" => "baz"}, @cache.read_multi('foo', 'fu'))
+    end
   end
 
   def test_fetch_multi
@@ -387,66 +388,74 @@ module CacheStoreBehavior
 
   def test_expires_in
     time = Time.local(2008, 4, 24)
-    Time.stubs(:now).returns(time)
 
-    @cache.write('foo', 'bar')
-    assert_equal 'bar', @cache.read('foo')
+    Time.stub(:now, time) do
+      @cache.write('foo', 'bar')
+      assert_equal 'bar', @cache.read('foo')
+    end
 
-    Time.stubs(:now).returns(time + 30)
-    assert_equal 'bar', @cache.read('foo')
+    Time.stub(:now, time + 30) do
+      assert_equal 'bar', @cache.read('foo')
+    end
 
-    Time.stubs(:now).returns(time + 61)
-    assert_nil @cache.read('foo')
+    Time.stub(:now, time + 61) do
+      assert_nil @cache.read('foo')
+    end
   end
 
   def test_race_condition_protection_skipped_if_not_defined
     @cache.write('foo', 'bar')
     time = @cache.send(:read_entry, 'foo', {}).expires_at
-    Time.stubs(:now).returns(Time.at(time))
 
-    result = @cache.fetch('foo') do
-      assert_equal nil, @cache.read('foo')
-      'baz'
+    Time.stub(:now, Time.at(time)) do
+      result = @cache.fetch('foo') do
+        assert_equal nil, @cache.read('foo')
+        'baz'
+      end
+      assert_equal 'baz', result
     end
-    assert_equal 'baz', result
   end
 
   def test_race_condition_protection_is_limited
     time = Time.now
     @cache.write('foo', 'bar', :expires_in => 60)
-    Time.stubs(:now).returns(time + 71)
-    result = @cache.fetch('foo', :race_condition_ttl => 10) do
-      assert_equal nil, @cache.read('foo')
-      "baz"
+    Time.stub(:now, time + 71) do
+      result = @cache.fetch('foo', :race_condition_ttl => 10) do
+        assert_equal nil, @cache.read('foo')
+        "baz"
+      end
+      assert_equal "baz", result
     end
-    assert_equal "baz", result
   end
 
   def test_race_condition_protection_is_safe
     time = Time.now
     @cache.write('foo', 'bar', :expires_in => 60)
-    Time.stubs(:now).returns(time + 61)
-    begin
-      @cache.fetch('foo', :race_condition_ttl => 10) do
-        assert_equal 'bar', @cache.read('foo')
-        raise ArgumentError.new
+    Time.stub(:now, time + 61) do
+      begin
+        @cache.fetch('foo', :race_condition_ttl => 10) do
+          assert_equal 'bar', @cache.read('foo')
+          raise ArgumentError.new
+        end
+      rescue ArgumentError
       end
-    rescue ArgumentError
+      assert_equal "bar", @cache.read('foo')
+    end
+    Time.stub(:now, time + 91) do
+      assert_nil @cache.read('foo')
     end
-    assert_equal "bar", @cache.read('foo')
-    Time.stubs(:now).returns(time + 91)
-    assert_nil @cache.read('foo')
   end
 
   def test_race_condition_protection
     time = Time.now
     @cache.write('foo', 'bar', :expires_in => 60)
-    Time.stubs(:now).returns(time + 61)
-    result = @cache.fetch('foo', :race_condition_ttl => 10) do
-      assert_equal 'bar', @cache.read('foo')
-      "baz"
+    Time.stub(:now, time + 61) do
+      result = @cache.fetch('foo', :race_condition_ttl => 10) do
+        assert_equal 'bar', @cache.read('foo')
+        "baz"
+      end
+      assert_equal "baz", result
     end
-    assert_equal "baz", result
   end
 
   def test_crazy_key_characters
@@ -775,11 +784,12 @@ class FileStoreTest < ActiveSupport::TestCase
     @cache.write('foo', 'bar', expires_in: 10)
     @cache.write('baz', 'qux')
     @cache.write('quux', 'corge', expires_in: 20)
-    Time.stubs(:now).returns(time + 15)
-    @cache.cleanup
-    assert_not @cache.exist?('foo')
-    assert @cache.exist?('baz')
-    assert @cache.exist?('quux')
+    Time.stub(:now, time + 15) do
+      @cache.cleanup
+      assert_not @cache.exist?('foo')
+      assert @cache.exist?('baz')
+      assert @cache.exist?('quux')
+    end
   end
 
   def test_write_with_unless_exist
@@ -1056,9 +1066,9 @@ class CacheEntryTest < ActiveSupport::TestCase
     assert !entry.expired?, 'entry not expired'
     entry = ActiveSupport::Cache::Entry.new("value", :expires_in => 60)
     assert !entry.expired?, 'entry not expired'
-    time = Time.now + 61
-    Time.stubs(:now).returns(time)
-    assert entry.expired?, 'entry is expired'
+    Time.stub(:now, Time.now + 61) do
+      assert entry.expired?, 'entry is expired'
+    end
   end
 
   def test_compress_values
diff --git a/activesupport/test/core_ext/date_ext_test.rb b/activesupport/test/core_ext/date_ext_test.rb
index e89be25b53..0fc3f765f5 100644
--- a/activesupport/test/core_ext/date_ext_test.rb
+++ b/activesupport/test/core_ext/date_ext_test.rb
@@ -191,8 +191,9 @@ class DateExtCalculationsTest < ActiveSupport::TestCase
   def test_yesterday_constructor_when_zone_is_set
     with_env_tz 'UTC' do
       with_tz_default ActiveSupport::TimeZone['Eastern Time (US & Canada)'] do # UTC -5
-        Time.stubs(:now).returns Time.local(2000, 1, 1)
-        assert_equal Date.new(1999, 12, 30), Date.yesterday
+        Time.stub(:now, Time.local(2000, 1, 1)) do
+          assert_equal Date.new(1999, 12, 30), Date.yesterday
+        end
       end
     end
   end
@@ -212,8 +213,9 @@ class DateExtCalculationsTest < ActiveSupport::TestCase
   def test_tomorrow_constructor_when_zone_is_set
     with_env_tz 'UTC' do
       with_tz_default ActiveSupport::TimeZone['Europe/Paris'] do # UTC +1
-        Time.stubs(:now).returns Time.local(1999, 12, 31, 23)
-        assert_equal Date.new(2000, 1, 2), Date.tomorrow
+        Time.stub(:now, Time.local(1999, 12, 31, 23)) do
+          assert_equal Date.new(2000, 1, 2), Date.tomorrow
+        end
       end
     end
   end
@@ -317,23 +319,26 @@ class DateExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_past
-    Date.stubs(:current).returns(Date.new(2000, 1, 1))
-    assert_equal true, Date.new(1999, 12, 31).past?
-    assert_equal false, Date.new(2000,1,1).past?
-    assert_equal false, Date.new(2000,1,2).past?
+    Date.stub(:current, Date.new(2000, 1, 1)) do
+      assert_equal true, Date.new(1999, 12, 31).past?
+      assert_equal false, Date.new(2000,1,1).past?
+      assert_equal false, Date.new(2000,1,2).past?
+    end
   end
 
   def test_future
-    Date.stubs(:current).returns(Date.new(2000, 1, 1))
-    assert_equal false, Date.new(1999, 12, 31).future?
-    assert_equal false, Date.new(2000,1,1).future?
-    assert_equal true, Date.new(2000,1,2).future?
+    Date.stub(:current, Date.new(2000, 1, 1)) do
+      assert_equal false, Date.new(1999, 12, 31).future?
+      assert_equal false, Date.new(2000,1,1).future?
+      assert_equal true, Date.new(2000,1,2).future?
+    end
   end
 
   def test_current_returns_date_today_when_zone_not_set
     with_env_tz 'US/Central' do
-      Time.stubs(:now).returns Time.local(1999, 12, 31, 23)
-      assert_equal Date.today, Date.current
+      Time.stub(:now, Time.local(1999, 12, 31, 23)) do
+        assert_equal Date.today, Date.current
+      end
     end
   end
 
diff --git a/activesupport/test/core_ext/date_time_ext_test.rb b/activesupport/test/core_ext/date_time_ext_test.rb
index 74319ecd09..58d79f0541 100644
--- a/activesupport/test/core_ext/date_time_ext_test.rb
+++ b/activesupport/test/core_ext/date_time_ext_test.rb
@@ -204,61 +204,69 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_today_with_offset
-    Date.stubs(:current).returns(Date.new(2000, 1, 1))
-    assert_equal false, DateTime.civil(1999,12,31,23,59,59, Rational(-18000, 86400)).today?
-    assert_equal true,  DateTime.civil(2000,1,1,0,0,0, Rational(-18000, 86400)).today?
-    assert_equal true,  DateTime.civil(2000,1,1,23,59,59, Rational(-18000, 86400)).today?
-    assert_equal false, DateTime.civil(2000,1,2,0,0,0, Rational(-18000, 86400)).today?
+    Date.stub(:current, Date.new(2000, 1, 1)) do
+      assert_equal false, DateTime.civil(1999,12,31,23,59,59, Rational(-18000, 86400)).today?
+      assert_equal true,  DateTime.civil(2000,1,1,0,0,0, Rational(-18000, 86400)).today?
+      assert_equal true,  DateTime.civil(2000,1,1,23,59,59, Rational(-18000, 86400)).today?
+      assert_equal false, DateTime.civil(2000,1,2,0,0,0, Rational(-18000, 86400)).today?
+    end
   end
 
   def test_today_without_offset
-    Date.stubs(:current).returns(Date.new(2000, 1, 1))
-    assert_equal false, DateTime.civil(1999,12,31,23,59,59).today?
-    assert_equal true,  DateTime.civil(2000,1,1,0).today?
-    assert_equal true,  DateTime.civil(2000,1,1,23,59,59).today?
-    assert_equal false, DateTime.civil(2000,1,2,0).today?
+    Date.stub(:current, Date.new(2000, 1, 1)) do
+      assert_equal false, DateTime.civil(1999,12,31,23,59,59).today?
+      assert_equal true,  DateTime.civil(2000,1,1,0).today?
+      assert_equal true,  DateTime.civil(2000,1,1,23,59,59).today?
+      assert_equal false, DateTime.civil(2000,1,2,0).today?
+    end
   end
 
   def test_past_with_offset
-    DateTime.stubs(:current).returns(DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400)))
-    assert_equal true,  DateTime.civil(2005,2,10,15,30,44, Rational(-18000, 86400)).past?
-    assert_equal false,  DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400)).past?
-    assert_equal false,  DateTime.civil(2005,2,10,15,30,46, Rational(-18000, 86400)).past?
+    DateTime.stub(:current, DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400))) do
+      assert_equal true,  DateTime.civil(2005,2,10,15,30,44, Rational(-18000, 86400)).past?
+      assert_equal false,  DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400)).past?
+      assert_equal false,  DateTime.civil(2005,2,10,15,30,46, Rational(-18000, 86400)).past?
+    end
   end
 
   def test_past_without_offset
-    DateTime.stubs(:current).returns(DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400)))
-    assert_equal true,  DateTime.civil(2005,2,10,20,30,44).past?
-    assert_equal false,  DateTime.civil(2005,2,10,20,30,45).past?
-    assert_equal false,  DateTime.civil(2005,2,10,20,30,46).past?
+    DateTime.stub(:current, DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400))) do
+      assert_equal true,  DateTime.civil(2005,2,10,20,30,44).past?
+      assert_equal false,  DateTime.civil(2005,2,10,20,30,45).past?
+      assert_equal false,  DateTime.civil(2005,2,10,20,30,46).past?
+    end
   end
 
   def test_future_with_offset
-    DateTime.stubs(:current).returns(DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400)))
-    assert_equal false,  DateTime.civil(2005,2,10,15,30,44, Rational(-18000, 86400)).future?
-    assert_equal false,  DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400)).future?
-    assert_equal true,  DateTime.civil(2005,2,10,15,30,46, Rational(-18000, 86400)).future?
+    DateTime.stub(:current, DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400))) do
+      assert_equal false,  DateTime.civil(2005,2,10,15,30,44, Rational(-18000, 86400)).future?
+      assert_equal false,  DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400)).future?
+      assert_equal true,  DateTime.civil(2005,2,10,15,30,46, Rational(-18000, 86400)).future?
+    end
   end
 
   def test_future_without_offset
-    DateTime.stubs(:current).returns(DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400)))
-    assert_equal false,  DateTime.civil(2005,2,10,20,30,44).future?
-    assert_equal false,  DateTime.civil(2005,2,10,20,30,45).future?
-    assert_equal true,  DateTime.civil(2005,2,10,20,30,46).future?
+    DateTime.stub(:current, DateTime.civil(2005,2,10,15,30,45, Rational(-18000, 86400))) do
+      assert_equal false,  DateTime.civil(2005,2,10,20,30,44).future?
+      assert_equal false,  DateTime.civil(2005,2,10,20,30,45).future?
+      assert_equal true,  DateTime.civil(2005,2,10,20,30,46).future?
+    end
   end
 
   def test_current_returns_date_today_when_zone_is_not_set
     with_env_tz 'US/Eastern' do
-      Time.stubs(:now).returns Time.local(1999, 12, 31, 23, 59, 59)
-      assert_equal DateTime.new(1999, 12, 31, 23, 59, 59, Rational(-18000, 86400)), DateTime.current
+      Time.stub(:now, Time.local(1999, 12, 31, 23, 59, 59)) do
+        assert_equal DateTime.new(1999, 12, 31, 23, 59, 59, Rational(-18000, 86400)), DateTime.current
+      end
     end
   end
 
   def test_current_returns_time_zone_today_when_zone_is_set
     Time.zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
     with_env_tz 'US/Eastern' do
-      Time.stubs(:now).returns Time.local(1999, 12, 31, 23, 59, 59)
-      assert_equal DateTime.new(1999, 12, 31, 23, 59, 59, Rational(-18000, 86400)), DateTime.current
+      Time.stub(:now, Time.local(1999, 12, 31, 23, 59, 59)) do
+        assert_equal DateTime.new(1999, 12, 31, 23, 59, 59, Rational(-18000, 86400)), DateTime.current
+      end
     end
   ensure
     Time.zone = nil
diff --git a/activesupport/test/core_ext/duration_test.rb b/activesupport/test/core_ext/duration_test.rb
index c283b546e6..9e97acaffb 100644
--- a/activesupport/test/core_ext/duration_test.rb
+++ b/activesupport/test/core_ext/duration_test.rb
@@ -140,28 +140,30 @@ class DurationTest < ActiveSupport::TestCase
   def test_since_and_ago_anchored_to_time_now_when_time_zone_is_not_set
     Time.zone = nil
     with_env_tz 'US/Eastern' do
-      Time.stubs(:now).returns Time.local(2000)
-      # since
-      assert_not_instance_of ActiveSupport::TimeWithZone, 5.seconds.since
-      assert_equal Time.local(2000,1,1,0,0,5), 5.seconds.since
-      # ago
-      assert_not_instance_of ActiveSupport::TimeWithZone, 5.seconds.ago
-      assert_equal Time.local(1999,12,31,23,59,55), 5.seconds.ago
+      Time.stub(:now, Time.local(2000)) do
+        # since
+        assert_not_instance_of ActiveSupport::TimeWithZone, 5.seconds.since
+        assert_equal Time.local(2000,1,1,0,0,5), 5.seconds.since
+        # ago
+        assert_not_instance_of ActiveSupport::TimeWithZone, 5.seconds.ago
+        assert_equal Time.local(1999,12,31,23,59,55), 5.seconds.ago
+      end
     end
   end
 
   def test_since_and_ago_anchored_to_time_zone_now_when_time_zone_is_set
     Time.zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
     with_env_tz 'US/Eastern' do
-      Time.stubs(:now).returns Time.local(2000)
-      # since
-      assert_instance_of ActiveSupport::TimeWithZone, 5.seconds.since
-      assert_equal Time.utc(2000,1,1,0,0,5), 5.seconds.since.time
-      assert_equal 'Eastern Time (US & Canada)', 5.seconds.since.time_zone.name
-      # ago
-      assert_instance_of ActiveSupport::TimeWithZone, 5.seconds.ago
-      assert_equal Time.utc(1999,12,31,23,59,55), 5.seconds.ago.time
-      assert_equal 'Eastern Time (US & Canada)', 5.seconds.ago.time_zone.name
+      Time.stub(:now, Time.local(2000)) do
+        # since
+        assert_instance_of ActiveSupport::TimeWithZone, 5.seconds.since
+        assert_equal Time.utc(2000,1,1,0,0,5), 5.seconds.since.time
+        assert_equal 'Eastern Time (US & Canada)', 5.seconds.since.time_zone.name
+        # ago
+        assert_instance_of ActiveSupport::TimeWithZone, 5.seconds.ago
+        assert_equal Time.utc(1999,12,31,23,59,55), 5.seconds.ago.time
+        assert_equal 'Eastern Time (US & Canada)', 5.seconds.ago.time_zone.name
+      end
     end
   ensure
     Time.zone = nil
diff --git a/activesupport/test/core_ext/string_ext_test.rb b/activesupport/test/core_ext/string_ext_test.rb
index cb24147ab3..3a5d6df06d 100644
--- a/activesupport/test/core_ext/string_ext_test.rb
+++ b/activesupport/test/core_ext/string_ext_test.rb
@@ -435,117 +435,123 @@ class StringConversionsTest < ActiveSupport::TestCase
 
   def test_standard_time_string_to_time_when_current_time_is_standard_time
     with_env_tz "US/Eastern" do
-      Time.stubs(:now).returns(Time.local(2012, 1, 1))
-      assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00".to_time
-      assert_equal Time.utc(2012, 1, 1, 10, 0), "2012-01-01 10:00".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 13, 0), "2012-01-01 10:00 -0800".to_time
-      assert_equal Time.utc(2012, 1, 1, 18, 0), "2012-01-01 10:00 -0800".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00 -0500".to_time
-      assert_equal Time.utc(2012, 1, 1, 15, 0), "2012-01-01 10:00 -0500".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 5, 0), "2012-01-01 10:00 UTC".to_time
-      assert_equal Time.utc(2012, 1, 1, 10, 0), "2012-01-01 10:00 UTC".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 13, 0), "2012-01-01 10:00 PST".to_time
-      assert_equal Time.utc(2012, 1, 1, 18, 0), "2012-01-01 10:00 PST".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00 EST".to_time
-      assert_equal Time.utc(2012, 1, 1, 15, 0), "2012-01-01 10:00 EST".to_time(:utc)
+      Time.stub(:now, Time.local(2012, 1, 1)) do
+        assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00".to_time
+        assert_equal Time.utc(2012, 1, 1, 10, 0), "2012-01-01 10:00".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 13, 0), "2012-01-01 10:00 -0800".to_time
+        assert_equal Time.utc(2012, 1, 1, 18, 0), "2012-01-01 10:00 -0800".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00 -0500".to_time
+        assert_equal Time.utc(2012, 1, 1, 15, 0), "2012-01-01 10:00 -0500".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 5, 0), "2012-01-01 10:00 UTC".to_time
+        assert_equal Time.utc(2012, 1, 1, 10, 0), "2012-01-01 10:00 UTC".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 13, 0), "2012-01-01 10:00 PST".to_time
+        assert_equal Time.utc(2012, 1, 1, 18, 0), "2012-01-01 10:00 PST".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00 EST".to_time
+        assert_equal Time.utc(2012, 1, 1, 15, 0), "2012-01-01 10:00 EST".to_time(:utc)
+      end
     end
   end
 
   def test_standard_time_string_to_time_when_current_time_is_daylight_savings
     with_env_tz "US/Eastern" do
-      Time.stubs(:now).returns(Time.local(2012, 7, 1))
-      assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00".to_time
-      assert_equal Time.utc(2012, 1, 1, 10, 0), "2012-01-01 10:00".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 13, 0), "2012-01-01 10:00 -0800".to_time
-      assert_equal Time.utc(2012, 1, 1, 18, 0), "2012-01-01 10:00 -0800".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00 -0500".to_time
-      assert_equal Time.utc(2012, 1, 1, 15, 0), "2012-01-01 10:00 -0500".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 5, 0), "2012-01-01 10:00 UTC".to_time
-      assert_equal Time.utc(2012, 1, 1, 10, 0), "2012-01-01 10:00 UTC".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 13, 0), "2012-01-01 10:00 PST".to_time
-      assert_equal Time.utc(2012, 1, 1, 18, 0), "2012-01-01 10:00 PST".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00 EST".to_time
-      assert_equal Time.utc(2012, 1, 1, 15, 0), "2012-01-01 10:00 EST".to_time(:utc)
+      Time.stub(:now, Time.local(2012, 7, 1)) do
+        assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00".to_time
+        assert_equal Time.utc(2012, 1, 1, 10, 0), "2012-01-01 10:00".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 13, 0), "2012-01-01 10:00 -0800".to_time
+        assert_equal Time.utc(2012, 1, 1, 18, 0), "2012-01-01 10:00 -0800".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00 -0500".to_time
+        assert_equal Time.utc(2012, 1, 1, 15, 0), "2012-01-01 10:00 -0500".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 5, 0), "2012-01-01 10:00 UTC".to_time
+        assert_equal Time.utc(2012, 1, 1, 10, 0), "2012-01-01 10:00 UTC".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 13, 0), "2012-01-01 10:00 PST".to_time
+        assert_equal Time.utc(2012, 1, 1, 18, 0), "2012-01-01 10:00 PST".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 10, 0), "2012-01-01 10:00 EST".to_time
+        assert_equal Time.utc(2012, 1, 1, 15, 0), "2012-01-01 10:00 EST".to_time(:utc)
+      end
     end
   end
 
   def test_daylight_savings_string_to_time_when_current_time_is_standard_time
     with_env_tz "US/Eastern" do
-      Time.stubs(:now).returns(Time.local(2012, 1, 1))
-      assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00".to_time
-      assert_equal Time.utc(2012, 7, 1, 10, 0), "2012-07-01 10:00".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 13, 0), "2012-07-01 10:00 -0700".to_time
-      assert_equal Time.utc(2012, 7, 1, 17, 0), "2012-07-01 10:00 -0700".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00 -0400".to_time
-      assert_equal Time.utc(2012, 7, 1, 14, 0), "2012-07-01 10:00 -0400".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 6, 0), "2012-07-01 10:00 UTC".to_time
-      assert_equal Time.utc(2012, 7, 1, 10, 0), "2012-07-01 10:00 UTC".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 13, 0), "2012-07-01 10:00 PDT".to_time
-      assert_equal Time.utc(2012, 7, 1, 17, 0), "2012-07-01 10:00 PDT".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00 EDT".to_time
-      assert_equal Time.utc(2012, 7, 1, 14, 0), "2012-07-01 10:00 EDT".to_time(:utc)
+      Time.stub(:now, Time.local(2012, 1, 1)) do
+        assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00".to_time
+        assert_equal Time.utc(2012, 7, 1, 10, 0), "2012-07-01 10:00".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 13, 0), "2012-07-01 10:00 -0700".to_time
+        assert_equal Time.utc(2012, 7, 1, 17, 0), "2012-07-01 10:00 -0700".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00 -0400".to_time
+        assert_equal Time.utc(2012, 7, 1, 14, 0), "2012-07-01 10:00 -0400".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 6, 0), "2012-07-01 10:00 UTC".to_time
+        assert_equal Time.utc(2012, 7, 1, 10, 0), "2012-07-01 10:00 UTC".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 13, 0), "2012-07-01 10:00 PDT".to_time
+        assert_equal Time.utc(2012, 7, 1, 17, 0), "2012-07-01 10:00 PDT".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00 EDT".to_time
+        assert_equal Time.utc(2012, 7, 1, 14, 0), "2012-07-01 10:00 EDT".to_time(:utc)
+      end
     end
   end
 
   def test_daylight_savings_string_to_time_when_current_time_is_daylight_savings
     with_env_tz "US/Eastern" do
-      Time.stubs(:now).returns(Time.local(2012, 7, 1))
-      assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00".to_time
-      assert_equal Time.utc(2012, 7, 1, 10, 0), "2012-07-01 10:00".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 13, 0), "2012-07-01 10:00 -0700".to_time
-      assert_equal Time.utc(2012, 7, 1, 17, 0), "2012-07-01 10:00 -0700".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00 -0400".to_time
-      assert_equal Time.utc(2012, 7, 1, 14, 0), "2012-07-01 10:00 -0400".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 6, 0), "2012-07-01 10:00 UTC".to_time
-      assert_equal Time.utc(2012, 7, 1, 10, 0), "2012-07-01 10:00 UTC".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 13, 0), "2012-07-01 10:00 PDT".to_time
-      assert_equal Time.utc(2012, 7, 1, 17, 0), "2012-07-01 10:00 PDT".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00 EDT".to_time
-      assert_equal Time.utc(2012, 7, 1, 14, 0), "2012-07-01 10:00 EDT".to_time(:utc)
+      Time.stub(:now, Time.local(2012, 7, 1)) do
+        assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00".to_time
+        assert_equal Time.utc(2012, 7, 1, 10, 0), "2012-07-01 10:00".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 13, 0), "2012-07-01 10:00 -0700".to_time
+        assert_equal Time.utc(2012, 7, 1, 17, 0), "2012-07-01 10:00 -0700".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00 -0400".to_time
+        assert_equal Time.utc(2012, 7, 1, 14, 0), "2012-07-01 10:00 -0400".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 6, 0), "2012-07-01 10:00 UTC".to_time
+        assert_equal Time.utc(2012, 7, 1, 10, 0), "2012-07-01 10:00 UTC".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 13, 0), "2012-07-01 10:00 PDT".to_time
+        assert_equal Time.utc(2012, 7, 1, 17, 0), "2012-07-01 10:00 PDT".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 10, 0), "2012-07-01 10:00 EDT".to_time
+        assert_equal Time.utc(2012, 7, 1, 14, 0), "2012-07-01 10:00 EDT".to_time(:utc)
+      end
     end
   end
 
   def test_partial_string_to_time_when_current_time_is_standard_time
     with_env_tz "US/Eastern" do
-      Time.stubs(:now).returns(Time.local(2012, 1, 1))
-      assert_equal Time.local(2012, 1, 1, 10, 0), "10:00".to_time
-      assert_equal Time.utc(2012, 1, 1, 10, 0),  "10:00".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 6, 0), "10:00 -0100".to_time
-      assert_equal Time.utc(2012, 1, 1, 11, 0), "10:00 -0100".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 10, 0), "10:00 -0500".to_time
-      assert_equal Time.utc(2012, 1, 1, 15, 0), "10:00 -0500".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 5, 0), "10:00 UTC".to_time
-      assert_equal Time.utc(2012, 1, 1, 10, 0), "10:00 UTC".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 13, 0), "10:00 PST".to_time
-      assert_equal Time.utc(2012, 1, 1, 18, 0), "10:00 PST".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 12, 0), "10:00 PDT".to_time
-      assert_equal Time.utc(2012, 1, 1, 17, 0), "10:00 PDT".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 10, 0), "10:00 EST".to_time
-      assert_equal Time.utc(2012, 1, 1, 15, 0), "10:00 EST".to_time(:utc)
-      assert_equal Time.local(2012, 1, 1, 9, 0), "10:00 EDT".to_time
-      assert_equal Time.utc(2012, 1, 1, 14, 0), "10:00 EDT".to_time(:utc)
+      Time.stub(:now, Time.local(2012, 1, 1)) do
+        assert_equal Time.local(2012, 1, 1, 10, 0), "10:00".to_time
+        assert_equal Time.utc(2012, 1, 1, 10, 0),  "10:00".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 6, 0), "10:00 -0100".to_time
+        assert_equal Time.utc(2012, 1, 1, 11, 0), "10:00 -0100".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 10, 0), "10:00 -0500".to_time
+        assert_equal Time.utc(2012, 1, 1, 15, 0), "10:00 -0500".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 5, 0), "10:00 UTC".to_time
+        assert_equal Time.utc(2012, 1, 1, 10, 0), "10:00 UTC".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 13, 0), "10:00 PST".to_time
+        assert_equal Time.utc(2012, 1, 1, 18, 0), "10:00 PST".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 12, 0), "10:00 PDT".to_time
+        assert_equal Time.utc(2012, 1, 1, 17, 0), "10:00 PDT".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 10, 0), "10:00 EST".to_time
+        assert_equal Time.utc(2012, 1, 1, 15, 0), "10:00 EST".to_time(:utc)
+        assert_equal Time.local(2012, 1, 1, 9, 0), "10:00 EDT".to_time
+        assert_equal Time.utc(2012, 1, 1, 14, 0), "10:00 EDT".to_time(:utc)
+      end
     end
   end
 
   def test_partial_string_to_time_when_current_time_is_daylight_savings
     with_env_tz "US/Eastern" do
-      Time.stubs(:now).returns(Time.local(2012, 7, 1))
-      assert_equal Time.local(2012, 7, 1, 10, 0), "10:00".to_time
-      assert_equal Time.utc(2012, 7, 1, 10, 0), "10:00".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 7, 0), "10:00 -0100".to_time
-      assert_equal Time.utc(2012, 7, 1, 11, 0), "10:00 -0100".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 11, 0), "10:00 -0500".to_time
-      assert_equal Time.utc(2012, 7, 1, 15, 0), "10:00 -0500".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 6, 0), "10:00 UTC".to_time
-      assert_equal Time.utc(2012, 7, 1, 10, 0), "10:00 UTC".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 14, 0), "10:00 PST".to_time
-      assert_equal Time.utc(2012, 7, 1, 18, 0), "10:00 PST".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 13, 0), "10:00 PDT".to_time
-      assert_equal Time.utc(2012, 7, 1, 17, 0), "10:00 PDT".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 11, 0), "10:00 EST".to_time
-      assert_equal Time.utc(2012, 7, 1, 15, 0), "10:00 EST".to_time(:utc)
-      assert_equal Time.local(2012, 7, 1, 10, 0), "10:00 EDT".to_time
-      assert_equal Time.utc(2012, 7, 1, 14, 0), "10:00 EDT".to_time(:utc)
+      Time.stub(:now, Time.local(2012, 7, 1)) do
+        assert_equal Time.local(2012, 7, 1, 10, 0), "10:00".to_time
+        assert_equal Time.utc(2012, 7, 1, 10, 0), "10:00".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 7, 0), "10:00 -0100".to_time
+        assert_equal Time.utc(2012, 7, 1, 11, 0), "10:00 -0100".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 11, 0), "10:00 -0500".to_time
+        assert_equal Time.utc(2012, 7, 1, 15, 0), "10:00 -0500".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 6, 0), "10:00 UTC".to_time
+        assert_equal Time.utc(2012, 7, 1, 10, 0), "10:00 UTC".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 14, 0), "10:00 PST".to_time
+        assert_equal Time.utc(2012, 7, 1, 18, 0), "10:00 PST".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 13, 0), "10:00 PDT".to_time
+        assert_equal Time.utc(2012, 7, 1, 17, 0), "10:00 PDT".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 11, 0), "10:00 EST".to_time
+        assert_equal Time.utc(2012, 7, 1, 15, 0), "10:00 EST".to_time(:utc)
+        assert_equal Time.local(2012, 7, 1, 10, 0), "10:00 EDT".to_time
+        assert_equal Time.utc(2012, 7, 1, 14, 0), "10:00 EDT".to_time(:utc)
+      end
     end
   end
 
diff --git a/activesupport/test/core_ext/time_ext_test.rb b/activesupport/test/core_ext/time_ext_test.rb
index 62868d146b..e1ac5b3d8d 100644
--- a/activesupport/test/core_ext/time_ext_test.rb
+++ b/activesupport/test/core_ext/time_ext_test.rb
@@ -605,13 +605,15 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_days_in_month_feb_in_common_year_without_year_arg
-    Time.stubs(:now).returns(Time.utc(2007))
-    assert_equal 28, Time.days_in_month(2)
+    Time.stub(:now, Time.utc(2007)) do
+      assert_equal 28, Time.days_in_month(2)
+    end
   end
 
   def test_days_in_month_feb_in_leap_year_without_year_arg
-    Time.stubs(:now).returns(Time.utc(2008))
-    assert_equal 29, Time.days_in_month(2)
+    Time.stub(:now, Time.utc(2008)) do
+      assert_equal 29, Time.days_in_month(2)
+    end
   end
 
   def test_last_month_on_31st
@@ -623,68 +625,74 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_today_with_time_local
-    Date.stubs(:current).returns(Date.new(2000, 1, 1))
-    assert_equal false, Time.local(1999,12,31,23,59,59).today?
-    assert_equal true,  Time.local(2000,1,1,0).today?
-    assert_equal true,  Time.local(2000,1,1,23,59,59).today?
-    assert_equal false, Time.local(2000,1,2,0).today?
+    Date.stub(:current, Date.new(2000, 1, 1)) do
+      assert_equal false, Time.local(1999,12,31,23,59,59).today?
+      assert_equal true,  Time.local(2000,1,1,0).today?
+      assert_equal true,  Time.local(2000,1,1,23,59,59).today?
+      assert_equal false, Time.local(2000,1,2,0).today?
+    end
   end
 
   def test_today_with_time_utc
-    Date.stubs(:current).returns(Date.new(2000, 1, 1))
-    assert_equal false, Time.utc(1999,12,31,23,59,59).today?
-    assert_equal true,  Time.utc(2000,1,1,0).today?
-    assert_equal true,  Time.utc(2000,1,1,23,59,59).today?
-    assert_equal false, Time.utc(2000,1,2,0).today?
+    Date.stub(:current, Date.new(2000, 1, 1)) do
+      assert_equal false, Time.utc(1999,12,31,23,59,59).today?
+      assert_equal true,  Time.utc(2000,1,1,0).today?
+      assert_equal true,  Time.utc(2000,1,1,23,59,59).today?
+      assert_equal false, Time.utc(2000,1,2,0).today?
+    end
   end
 
   def test_past_with_time_current_as_time_local
     with_env_tz 'US/Eastern' do
-      Time.stubs(:current).returns(Time.local(2005,2,10,15,30,45))
-      assert_equal true,  Time.local(2005,2,10,15,30,44).past?
-      assert_equal false,  Time.local(2005,2,10,15,30,45).past?
-      assert_equal false,  Time.local(2005,2,10,15,30,46).past?
-      assert_equal true,  Time.utc(2005,2,10,20,30,44).past?
-      assert_equal false,  Time.utc(2005,2,10,20,30,45).past?
-      assert_equal false,  Time.utc(2005,2,10,20,30,46).past?
+      Time.stub(:current, Time.local(2005,2,10,15,30,45)) do
+        assert_equal true,  Time.local(2005,2,10,15,30,44).past?
+        assert_equal false,  Time.local(2005,2,10,15,30,45).past?
+        assert_equal false,  Time.local(2005,2,10,15,30,46).past?
+        assert_equal true,  Time.utc(2005,2,10,20,30,44).past?
+        assert_equal false,  Time.utc(2005,2,10,20,30,45).past?
+        assert_equal false,  Time.utc(2005,2,10,20,30,46).past?
+      end
     end
   end
 
   def test_past_with_time_current_as_time_with_zone
     with_env_tz 'US/Eastern' do
       twz = Time.utc(2005,2,10,15,30,45).in_time_zone('Central Time (US & Canada)')
-      Time.stubs(:current).returns(twz)
-      assert_equal true,  Time.local(2005,2,10,10,30,44).past?
-      assert_equal false,  Time.local(2005,2,10,10,30,45).past?
-      assert_equal false,  Time.local(2005,2,10,10,30,46).past?
-      assert_equal true,  Time.utc(2005,2,10,15,30,44).past?
-      assert_equal false,  Time.utc(2005,2,10,15,30,45).past?
-      assert_equal false,  Time.utc(2005,2,10,15,30,46).past?
+      Time.stub(:current, twz) do
+        assert_equal true,  Time.local(2005,2,10,10,30,44).past?
+        assert_equal false,  Time.local(2005,2,10,10,30,45).past?
+        assert_equal false,  Time.local(2005,2,10,10,30,46).past?
+        assert_equal true,  Time.utc(2005,2,10,15,30,44).past?
+        assert_equal false,  Time.utc(2005,2,10,15,30,45).past?
+        assert_equal false,  Time.utc(2005,2,10,15,30,46).past?
+      end
     end
   end
 
   def test_future_with_time_current_as_time_local
     with_env_tz 'US/Eastern' do
-      Time.stubs(:current).returns(Time.local(2005,2,10,15,30,45))
-      assert_equal false,  Time.local(2005,2,10,15,30,44).future?
-      assert_equal false,  Time.local(2005,2,10,15,30,45).future?
-      assert_equal true,  Time.local(2005,2,10,15,30,46).future?
-      assert_equal false,  Time.utc(2005,2,10,20,30,44).future?
-      assert_equal false,  Time.utc(2005,2,10,20,30,45).future?
-      assert_equal true,  Time.utc(2005,2,10,20,30,46).future?
+      Time.stub(:current, Time.local(2005,2,10,15,30,45)) do
+        assert_equal false,  Time.local(2005,2,10,15,30,44).future?
+        assert_equal false,  Time.local(2005,2,10,15,30,45).future?
+        assert_equal true,  Time.local(2005,2,10,15,30,46).future?
+        assert_equal false,  Time.utc(2005,2,10,20,30,44).future?
+        assert_equal false,  Time.utc(2005,2,10,20,30,45).future?
+        assert_equal true,  Time.utc(2005,2,10,20,30,46).future?
+      end
     end
   end
 
   def test_future_with_time_current_as_time_with_zone
     with_env_tz 'US/Eastern' do
       twz = Time.utc(2005,2,10,15,30,45).in_time_zone('Central Time (US & Canada)')
-      Time.stubs(:current).returns(twz)
-      assert_equal false,  Time.local(2005,2,10,10,30,44).future?
-      assert_equal false,  Time.local(2005,2,10,10,30,45).future?
-      assert_equal true,  Time.local(2005,2,10,10,30,46).future?
-      assert_equal false,  Time.utc(2005,2,10,15,30,44).future?
-      assert_equal false,  Time.utc(2005,2,10,15,30,45).future?
-      assert_equal true,  Time.utc(2005,2,10,15,30,46).future?
+      Time.stub(:current, twz) do
+        assert_equal false,  Time.local(2005,2,10,10,30,44).future?
+        assert_equal false,  Time.local(2005,2,10,10,30,45).future?
+        assert_equal true,  Time.local(2005,2,10,10,30,46).future?
+        assert_equal false,  Time.utc(2005,2,10,15,30,44).future?
+        assert_equal false,  Time.utc(2005,2,10,15,30,45).future?
+        assert_equal true,  Time.utc(2005,2,10,15,30,46).future?
+      end
     end
   end
 
diff --git a/activesupport/test/core_ext/time_with_zone_test.rb b/activesupport/test/core_ext/time_with_zone_test.rb
index 79d78c02cd..5b48bf328c 100644
--- a/activesupport/test/core_ext/time_with_zone_test.rb
+++ b/activesupport/test/core_ext/time_with_zone_test.rb
@@ -205,45 +205,50 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_today
-    Date.stubs(:current).returns(Date.new(2000, 1, 1))
-    assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.utc(1999,12,31,23,59,59) ).today?
-    assert_equal true,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.utc(2000,1,1,0) ).today?
-    assert_equal true,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.utc(2000,1,1,23,59,59) ).today?
-    assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.utc(2000,1,2,0) ).today?
+    Date.stub(:current, Date.new(2000, 1, 1)) do
+      assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.utc(1999,12,31,23,59,59) ).today?
+      assert_equal true, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.utc(2000,1,1,0) ).today?
+      assert_equal true, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.utc(2000,1,1,23,59,59) ).today?
+      assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.utc(2000,1,2,0) ).today?
+    end
   end
 
   def test_past_with_time_current_as_time_local
     with_env_tz 'US/Eastern' do
-      Time.stubs(:current).returns(Time.local(2005,2,10,15,30,45))
-      assert_equal true,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,44)).past?
-      assert_equal false,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,45)).past?
-      assert_equal false,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,46)).past?
+      Time.stub(:current, Time.local(2005,2,10,15,30,45)) do
+        assert_equal true, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,44)).past?
+        assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,45)).past?
+        assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,46)).past?
+      end
     end
   end
 
   def test_past_with_time_current_as_time_with_zone
     twz = ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,45) )
-    Time.stubs(:current).returns(twz)
-    assert_equal true,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,44)).past?
-    assert_equal false,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,45)).past?
-    assert_equal false,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,46)).past?
+    Time.stub(:current, twz) do
+      assert_equal true, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,44)).past?
+      assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,45)).past?
+      assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,46)).past?
+    end
   end
 
   def test_future_with_time_current_as_time_local
     with_env_tz 'US/Eastern' do
-      Time.stubs(:current).returns(Time.local(2005,2,10,15,30,45))
-      assert_equal false,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,44)).future?
-      assert_equal false,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,45)).future?
-      assert_equal true,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,46)).future?
+      Time.stub(:current, Time.local(2005,2,10,15,30,45)) do
+        assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,44)).future?
+        assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,45)).future?
+        assert_equal true, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,46)).future?
+      end
     end
   end
 
   def test_future_with_time_current_as_time_with_zone
     twz = ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,45) )
-    Time.stubs(:current).returns(twz)
-    assert_equal false,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,44)).future?
-    assert_equal false,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,45)).future?
-    assert_equal true,  ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,46)).future?
+    Time.stub(:current, twz) do
+      assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,44)).future?
+      assert_equal false, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,45)).future?
+      assert_equal true, ActiveSupport::TimeWithZone.new( nil, @time_zone, Time.local(2005,2,10,15,30,46)).future?
+    end
   end
 
   def test_eql?
@@ -1033,19 +1038,21 @@ class TimeWithZoneMethodsForTimeAndDateTimeTest < ActiveSupport::TestCase
 
   def test_current_returns_time_now_when_zone_not_set
     with_env_tz 'US/Eastern' do
-      Time.stubs(:now).returns Time.local(2000)
-      assert_equal false, Time.current.is_a?(ActiveSupport::TimeWithZone)
-      assert_equal Time.local(2000), Time.current
+      Time.stub(:now, Time.local(2000)) do
+        assert_equal false, Time.current.is_a?(ActiveSupport::TimeWithZone)
+        assert_equal Time.local(2000), Time.current
+      end
     end
   end
 
   def test_current_returns_time_zone_now_when_zone_set
     Time.zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
     with_env_tz 'US/Eastern' do
-      Time.stubs(:now).returns Time.local(2000)
-      assert_equal true, Time.current.is_a?(ActiveSupport::TimeWithZone)
-      assert_equal 'Eastern Time (US & Canada)', Time.current.time_zone.name
-      assert_equal Time.utc(2000), Time.current.time
+      Time.stub(:now, Time.local(2000)) do
+        assert_equal true, Time.current.is_a?(ActiveSupport::TimeWithZone)
+        assert_equal 'Eastern Time (US & Canada)', Time.current.time_zone.name
+        assert_equal Time.utc(2000), Time.current.time
+      end
     end
   end
 
diff --git a/activesupport/test/time_travel_test.rb b/activesupport/test/time_travel_test.rb
index 869bc09991..59c3e52c2f 100644
--- a/activesupport/test/time_travel_test.rb
+++ b/activesupport/test/time_travel_test.rb
@@ -3,80 +3,88 @@ require 'active_support/core_ext/date_time'
 require 'active_support/core_ext/numeric/time'
 
 class TimeTravelTest < ActiveSupport::TestCase
-  setup do
-    Time.stubs now: Time.now
-  end
-
   teardown do
     travel_back
   end
 
   def test_time_helper_travel
-    expected_time = Time.now + 1.day
-    travel 1.day
+    Time.stub(:now, Time.now) do
+      expected_time = Time.now + 1.day
+      travel 1.day
 
-    assert_equal expected_time.to_s(:db), Time.now.to_s(:db)
-    assert_equal expected_time.to_date, Date.today
-    assert_equal expected_time.to_datetime.to_s(:db), DateTime.now.to_s(:db)
-  end
-
-  def test_time_helper_travel_with_block
-    expected_time = Time.now + 1.day
-
-    travel 1.day do
       assert_equal expected_time.to_s(:db), Time.now.to_s(:db)
       assert_equal expected_time.to_date, Date.today
       assert_equal expected_time.to_datetime.to_s(:db), DateTime.now.to_s(:db)
     end
+  end
 
-    assert_not_equal expected_time.to_s(:db), Time.now.to_s(:db)
-    assert_not_equal expected_time.to_date, Date.today
-    assert_not_equal expected_time.to_datetime.to_s(:db), DateTime.now.to_s(:db)
+  def test_time_helper_travel_with_block
+    Time.stub(:now, Time.now) do
+      expected_time = Time.now + 1.day
+
+      travel 1.day do
+        assert_equal expected_time.to_s(:db), Time.now.to_s(:db)
+        assert_equal expected_time.to_date, Date.today
+        assert_equal expected_time.to_datetime.to_s(:db), DateTime.now.to_s(:db)
+      end
+
+      assert_not_equal expected_time.to_s(:db), Time.now.to_s(:db)
+      assert_not_equal expected_time.to_date, Date.today
+      assert_not_equal expected_time.to_datetime.to_s(:db), DateTime.now.to_s(:db)
+    end
   end
 
   def test_time_helper_travel_to
-    expected_time = Time.new(2004, 11, 24, 01, 04, 44)
-    travel_to expected_time
+    Time.stub(:now, Time.now) do
+      expected_time = Time.new(2004, 11, 24, 01, 04, 44)
+      travel_to expected_time
 
-    assert_equal expected_time, Time.now
-    assert_equal Date.new(2004, 11, 24), Date.today
-    assert_equal expected_time.to_datetime, DateTime.now
-  end
-
-  def test_time_helper_travel_to_with_block
-    expected_time = Time.new(2004, 11, 24, 01, 04, 44)
-
-    travel_to expected_time do
       assert_equal expected_time, Time.now
       assert_equal Date.new(2004, 11, 24), Date.today
       assert_equal expected_time.to_datetime, DateTime.now
     end
+  end
 
-    assert_not_equal expected_time, Time.now
-    assert_not_equal Date.new(2004, 11, 24), Date.today
-    assert_not_equal expected_time.to_datetime, DateTime.now
+  def test_time_helper_travel_to_with_block
+    Time.stub(:now, Time.now) do
+      expected_time = Time.new(2004, 11, 24, 01, 04, 44)
+
+      travel_to expected_time do
+        assert_equal expected_time, Time.now
+        assert_equal Date.new(2004, 11, 24), Date.today
+        assert_equal expected_time.to_datetime, DateTime.now
+      end
+
+      assert_not_equal expected_time, Time.now
+      assert_not_equal Date.new(2004, 11, 24), Date.today
+      assert_not_equal expected_time.to_datetime, DateTime.now
+    end
   end
 
   def test_time_helper_travel_back
-    expected_time = Time.new(2004, 11, 24, 01, 04, 44)
+    Time.stub(:now, Time.now) do
+      expected_time = Time.new(2004, 11, 24, 01, 04, 44)
 
-    travel_to expected_time
-    assert_equal expected_time, Time.now
-    assert_equal Date.new(2004, 11, 24), Date.today
-    assert_equal expected_time.to_datetime, DateTime.now
-    travel_back
+      travel_to expected_time
+      assert_equal expected_time, Time.now
+      assert_equal Date.new(2004, 11, 24), Date.today
+      assert_equal expected_time.to_datetime, DateTime.now
+      travel_back
 
-    assert_not_equal expected_time, Time.now
-    assert_not_equal Date.new(2004, 11, 24), Date.today
-    assert_not_equal expected_time.to_datetime, DateTime.now
+      assert_not_equal expected_time, Time.now
+      assert_not_equal Date.new(2004, 11, 24), Date.today
+      assert_not_equal expected_time.to_datetime, DateTime.now
+    end
   end
 
   def test_travel_to_will_reset_the_usec_to_avoid_mysql_rouding
-    travel_to Time.utc(2014, 10, 10, 10, 10, 50, 999999) do
-      assert_equal 50, Time.now.sec
-      assert_equal 0, Time.now.usec
-      assert_equal 50, DateTime.now.sec
-      assert_equal 0, DateTime.now.usec
+    Time.stub(:now, Time.now) do
+      travel_to Time.utc(2014, 10, 10, 10, 10, 50, 999999) do
+        assert_equal 50, Time.now.sec
+        assert_equal 0, Time.now.usec
+        assert_equal 50, DateTime.now.sec
+        assert_equal 0, DateTime.now.usec
+      end
     end
   end
 end
diff --git a/activesupport/test/time_zone_test.rb b/activesupport/test/time_zone_test.rb
index 5e0474f449..34bb0e2995 100644
--- a/activesupport/test/time_zone_test.rb
+++ b/activesupport/test/time_zone_test.rb
@@ -252,9 +252,10 @@ class TimeZoneTest < ActiveSupport::TestCase
 
   def test_parse_with_incomplete_date
     zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
-    zone.stubs(:now).returns zone.local(1999,12,31)
-    twz = zone.parse('19:00:00')
-    assert_equal Time.utc(1999,12,31,19), twz.time
+    zone.stub(:now, zone.local(1999,12,31)) do
+      twz = zone.parse('19:00:00')
+      assert_equal Time.utc(1999,12,31,19), twz.time
+    end
   end
 
   def test_parse_with_day_omitted
@@ -284,9 +285,10 @@ class TimeZoneTest < ActiveSupport::TestCase
 
   def test_parse_with_missing_time_components
     zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
-    zone.stubs(:now).returns zone.local(1999, 12, 31, 12, 59, 59)
-    twz = zone.parse('2012-12-01')
-    assert_equal Time.utc(2012, 12, 1), twz.time
+    zone.stub(:now, zone.local(1999, 12, 31, 12, 59, 59)) do
+      twz = zone.parse('2012-12-01')
+      assert_equal Time.utc(2012, 12, 1), twz.time
+    end
   end
 
   def test_parse_with_javascript_date