Test Last-Modified header of api show element responses

test/controllers/api/nodes_controller_test.rb

@@ -204,8 +204,13 @@ module Api
     end
 
     def test_show
-      get api_node_path(create(:node))
+      node = create(:node, :timestamp => "2021-02-03T00:00:00Z")
+
+      get api_node_path(node)
+
       assert_response :success
+      assert_not_nil @response.header["Last-Modified"]
+      assert_equal "2021-02-03T00:00:00Z", Time.parse(@response.header["Last-Modified"]).utc.xmlschema
     end
 
     # Ensure the lat/lon is formatted as a decimal e.g. not 4.0e-05

test/controllers/api/relations_controller_test.rb

@@ -133,13 +133,15 @@ module Api
     end
 
     def test_show
-      relation = create(:relation)
+      relation = create(:relation, :timestamp => "2021-02-03T00:00:00Z")
-      node = create(:node)
+      node = create(:node, :timestamp => "2021-04-05T00:00:00Z")
       create(:relation_member, :relation => relation, :member => node)
 
       get api_relation_path(relation)
 
       assert_response :success
+      assert_not_nil @response.header["Last-Modified"]
+      assert_equal "2021-02-03T00:00:00Z", Time.parse(@response.header["Last-Modified"]).utc.xmlschema
       assert_dom "node", :count => 0
       assert_dom "relation", :count => 1 do
         assert_dom "> @id", :text => relation.id.to_s

test/controllers/api/ways_controller_test.rb

@@ -107,8 +107,15 @@ module Api
     end
 
     def test_show
-      get api_way_path(create(:way))
+      way = create(:way, :timestamp => "2021-02-03T00:00:00Z")
+      node = create(:node, :timestamp => "2021-04-05T00:00:00Z")
+      create(:way_node, :way => way, :node => node)
+
+      get api_way_path(way)
+
       assert_response :success
+      assert_not_nil @response.header["Last-Modified"]
+      assert_equal "2021-02-03T00:00:00Z", Time.parse(@response.header["Last-Modified"]).utc.xmlschema
     end
 
     def test_show_json