ignore timestamps if they have been set earlier

lib/simple_states/event.rb

@@ -30,20 +30,17 @@ def run_callbacks(type, obj, data)
       end
 
       def set_attrs(obj, data)
-        target_state_attr = "#{target_state(data)}_at"
-        attrs = { :"#{target_state_attr}" => Time.now.utc }.merge(data)
-        attrs.each do |key, value|
-          set_attr(obj, key, value) if set_timestamp?(key.to_s, target_state_attr)
-        end
+        attrs = { :"#{target_state(data)}_at" => Time.now.utc }.merge(data)
+        attrs.each { |key, value| set_attr(obj, key, value) }
         obj.state = target_state(data)
       end
 
       def set_attr(obj, key, value)
-        obj.send(:"#{key}=", value) if obj.respond_to?(:"#{key}=")
+        obj.send(:"#{key}=", value) if obj.respond_to?(:"#{key}=") and not has_timestamp?(obj, key)
       end
 
-      def set_timestamp?(key, target_state_attr)
-        key == target_state_attr || key == "finished_at" || !key.end_with?('at')
+      def has_timestamp?(obj, key)
+        key.to_s.end_with?('_at') && obj.respond_to?(key) && obj.send(key)
       end
 
       def ordered?(obj, data)

spec/events_spec.rb

@@ -40,10 +40,22 @@
   end
 
   describe 'ignores timestamp' do
-    describe 'when started_at timestamp is passed on a finish event' do
-      let(:attrs) { { finished_at: now - 50,  started_at: now - 60, state: "passed" } }
-      it { expect { obj.finish(attrs) }.to change { obj.finished_at }.to(attrs[:finished_at]) }
-      it { expect { obj.finish(attrs) }.to_not change { obj.started_at }}
+    describe 'when started_at had been set earlier' do
+      let(:attrs) { { started_at: now - 60, finished_at: now - 50, state: "passed" } }
+      let(:early) { now - 55 }
+      before      { obj.started_at = early }
+      before      { obj.finish(attrs) }
+      it { expect(obj.started_at).to eq early }
+      it { expect(obj.finished_at).to eq attrs[:finished_at] }
+    end
+
+    describe 'when finished_at had been set earlier' do
+      let(:attrs) { { started_at: now - 60, finished_at: now - 50, state: "passed" } }
+      let(:early) { now - 45 }
+      before      { obj.finished_at = early }
+      before      { obj.finish(attrs) }
+      it { expect(obj.started_at).to eq attrs[:started_at] }
+      it { expect(obj.finished_at).to eq early }
     end
   end