Add command to tag cards

test/models/command/filter_by_tag_test.rb

@@ -7,7 +7,7 @@ class Command::FilterByCardTest < ActionDispatch::IntegrationTest
     @tag = tags(:web)
   end
 
-  test "redirects to the cards index filtering by cards" do
+  test "redirect to the cards index filtering by cards" do
     result = execute_command "##{@tag.title}"
 
     assert_equal cards_path(indexed_by: "newest", tag_ids: [ @tag.id ]), result.url

test/models/command/tag_test.rb

@@ -0,0 +1,47 @@
+require "test_helper"
+
+class Command::TagTest < ActionDispatch::IntegrationTest
+  include CommandTestHelper
+
+  setup do
+    Current.session = sessions(:david)
+    @card = cards(:text)
+    @tag = tags(:web)
+  end
+
+  test "tag card on perma with existing tag" do
+    assert_changes -> { @card.tagged_with?(@tag) }, from: false, to: true do
+      execute_command "/tag #{@tag.title}", context_url: collection_card_url(@card.collection, @card)
+    end
+  end
+
+  test "tag card on perma with new card" do
+    assert_difference -> { @card.tags.count }, +1 do
+      execute_command "/tag some-new-tag", context_url: collection_card_url(@card.collection, @card)
+    end
+
+    assert_equal "some-new-tag", @card.tags.last.title
+  end
+
+  test "tag several cards on cards' index page" do
+    cards = cards(:logo, :text, :layout)
+    cards.each { it.taggings.destroy_all }
+
+    execute_command "/tag #{@tag.title}", context_url: collection_cards_url(@card.collection)
+
+    cards.each { assert it.reload.tagged_with?(@tag) }
+  end
+
+  test "undo tagged cards" do
+    cards = cards(:logo, :text, :layout)
+    cards.each { it.taggings.destroy_all }
+
+    command = parse_command "/tag #{@tag.title}", context_url: collection_cards_url(@card.collection)
+    command.execute
+
+    cards.each { assert it.reload.tagged_with?(@tag) }
+
+    command.undo
+    cards.each { assert_not it.reload.tagged_with?(@tag) }
+  end
+end