The params that come from the selected topics on the forum show page …

…are params[:moderated_topics]. Use these.

app/controllers/moderator/topics_controller.rb

@@ -13,7 +13,13 @@ def destroy
   #
   # The second comes from forums/show which will use all the currently selected moderations as the objects.
   def moderate
-    @moderations = Moderation.for_user(current_user).topics.find(params[:moderation_ids]) if params[:moderation_ids]
+    # Topics
+    @moderations = Topic.find(params[:moderated_topics], :include => :moderations).each do |topic|
+      topic.moderations.find_or_create_by_user_id(current_user.id)
+    end if params[:moderated_topics]
+    # Moderation objects
+    @moderations ||= Moderation.for_user(current_user).topics.find(params[:moderation_ids]) if params[:moderation_ids]
+    # All moderations for the current user.
     @moderations ||= Moderation.topics.for_user(current_user.id)
     case params[:commit]
       when "Lock"

features/step_definitions/topics_steps.rb

@@ -0,0 +1,8 @@
+Then /^I should see (\d+) sticky topics?$/ do |num|
+  Nokogiri::HTML(response.body).xpath("//img[@src]").select { |i| i['src'].match(/sticky/) }.size.should eql(num.to_i)
+end
+
+Then /^I should see (\d+) locked topics?$/ do |num|
+  p Topic.all.map(&:locked)
+  Nokogiri::HTML(response.body).xpath("//img[@src]").select { |i| i['src'].match(/locked/) }.size.should eql(num.to_i)
+end

features/topics_moderation.feature

@@ -0,0 +1,17 @@
+Feature: Topics moderation
+  In order to lock, delete, sticky and merge topics
+  As a person who's able to do that
+  I want the buttons to work for me
+
+  Background:
+    Given there is the usual setup
+
+  Scenario: Locking selected topics
+    Given I am logged in as "administrator" with the password "godly"
+    And I am on the homepage
+    When I follow "Public Forum"
+    Then I should see 0 locked topics
+    When I select "Default topic" for moderation
+    And I press "Lock"
+    Then I should see "All selected topics have been locked."
+    Then I should see 1 locked topic