Set timestamps before clearing changes

e7f66fb2 fixed one problem and introduced a new one. Setting timestamps
after clearing_changes_information doesn't work, since using the
created_at and updated_at setters will change the object again. I added
some additional specs for this case (our only spec related to clearing
changes used an object without timestamps).

For the timezone problem, I did a little digging and realized the
casting behavior was actually correct. The reason it was behaving in a
different way than I was expecting is because we had
`time_zone_aware_attributes` set to false, whereas the AR railtie
[sets it to true](54652d886a/activerecord/lib/active_record/railtie.rb (L71)). Setting it to true causes date and datetime attributes
[to get decorated with a TimeZoneConverter](54652d886a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb (L68..L87))

lib/factory_bot/strategy/stub.rb

@@ -31,8 +31,8 @@ module FactoryBot
       def result(evaluation)
         evaluation.object.tap do |instance|
           stub_database_interaction_on_result(instance)
-          clear_changes_information(instance)
           set_timestamps(instance)
+          clear_changes_information(instance)
           evaluation.notify(:after_stub, instance)
         end
       end

spec/acceptance/build_stubbed_spec.rb

@@ -156,14 +156,9 @@ describe "defaulting `created_at`" do
     expect(build_stubbed(:thing_with_timestamp).created_at).to eq Time.now
   end
 
-  it "defaults created_at for objects with created_at to the correct time with zone" do
+  it "is doesn't mark the object as changed" do
-    original_timezone = ENV["TZ"]
+    stub = build_stubbed(:thing_with_timestamp)
-    ENV["TZ"] = "UTC"
+    expect(stub).not_to be_changed
-    Time.zone = "Eastern Time (US & Canada)"
-
-    expect(build_stubbed(:thing_with_timestamp).created_at.zone).to eq "EST"
-
-    ENV["TZ"] = original_timezone
   end
 
   it "doesn't add created_at to objects who don't have the method" do
@@ -172,7 +167,9 @@ describe "defaulting `created_at`" do
   end
 
   it "allows overriding created_at for objects with created_at" do
-    expect(build_stubbed(:thing_with_timestamp, created_at: 3.days.ago).created_at).to eq 3.days.ago
+    created_at = 3.days.ago
+    stubbed = build_stubbed(:thing_with_timestamp, created_at: created_at)
+    expect(stubbed.created_at).to eq created_at
   end
 
   it "doesn't allow setting created_at on an object that doesn't define it" do
@@ -186,6 +183,48 @@ describe "defaulting `created_at`" do
     stub.created_at = 3.days.ago
     expect(stub.created_at).to eq 3.days.ago
   end
+
+  context "when using time_zone_aware_attributes" do
+    it "defaults created_at to the local time zone" do
+      Time.zone = "Eastern Time (US & Canada)"
+      ActiveRecord::Base.time_zone_aware_attributes = true
+
+      stub = build_stubbed(:thing_with_timestamp)
+
+      expect(stub.created_at.zone).to eq "EST"
+    end
+
+    it "casts created_at override to local time zone" do
+      Time.zone = "Eastern Time (US & Canada)"
+      ActiveRecord::Base.time_zone_aware_attributes = true
+      created_at = Time.now.in_time_zone("CET")
+
+      stub = build_stubbed(:thing_with_timestamp, created_at: created_at)
+
+      expect(stub.created_at.zone).to eq "EST"
+    end
+  end
+
+  context "when NOT using time_zone_aware_attributes" do
+    it "defaults created_at to UTC" do
+      Time.zone = "Eastern Time (US & Canada)"
+      ActiveRecord::Base.time_zone_aware_attributes = false
+
+      stub = build_stubbed(:thing_with_timestamp)
+
+      expect(stub.created_at.zone).to eq "UTC"
+    end
+
+    it "casts created_at override to UTC" do
+      Time.zone = "Eastern Time (US & Canada)"
+      ActiveRecord::Base.time_zone_aware_attributes = false
+      created_at = Time.now.in_time_zone("CET")
+
+      stub = build_stubbed(:thing_with_timestamp, created_at: created_at)
+
+      expect(stub.created_at.zone).to eq "UTC"
+    end
+  end
 end
 
 describe "defaulting `updated_at`" do
@@ -207,6 +246,11 @@ describe "defaulting `updated_at`" do
     expect(build_stubbed(:thing_with_timestamp).updated_at).to eq Time.current
   end
 
+  it "is doesn't mark the object as changed" do
+    stub = build_stubbed(:thing_with_timestamp)
+    expect(stub).not_to be_changed
+  end
+
   it "doesn't add updated_at to objects who don't have the method" do
     expect(build_stubbed(:thing_without_timestamp)).
       not_to respond_to(:updated_at)
@@ -229,6 +273,48 @@ describe "defaulting `updated_at`" do
     stub.updated_at = 3.days.ago
     expect(stub.updated_at).to eq 3.days.ago
   end
+
+  context "when using time_zone_aware_attributes" do
+    it "defaults updated_at to the local time zone" do
+      Time.zone = "Eastern Time (US & Canada)"
+      ActiveRecord::Base.time_zone_aware_attributes = true
+
+      stub = build_stubbed(:thing_with_timestamp)
+
+      expect(stub.updated_at.zone).to eq "EST"
+    end
+
+    it "casts updated_at override to local time zone" do
+      Time.zone = "Eastern Time (US & Canada)"
+      ActiveRecord::Base.time_zone_aware_attributes = true
+      updated_at = Time.now.in_time_zone("CET")
+
+      stub = build_stubbed(:thing_with_timestamp, updated_at: updated_at)
+
+      expect(stub.updated_at.zone).to eq "EST"
+    end
+  end
+
+  context "when NOT using time_zone_aware_attributes" do
+    it "defaults updated_at to UTC" do
+      Time.zone = "Eastern Time (US & Canada)"
+      ActiveRecord::Base.time_zone_aware_attributes = false
+
+      stub = build_stubbed(:thing_with_timestamp)
+
+      expect(stub.updated_at.zone).to eq "UTC"
+    end
+
+    it "casts updated_at override to UTC" do
+      Time.zone = "Eastern Time (US & Canada)"
+      ActiveRecord::Base.time_zone_aware_attributes = false
+      updated_at = Time.now.in_time_zone("CET")
+
+      stub = build_stubbed(:thing_with_timestamp, updated_at: updated_at)
+
+      expect(stub.updated_at.zone).to eq "UTC"
+    end
+  end
 end
 
 describe "defaulting `id`" do