FIX: suggested topics sometimes adds new topics from other categories before new topics of the current category

lib/suggested_topics_builder.rb

@@ -31,14 +31,19 @@ class SuggestedTopicsBuilder
   end
 
   def splice_results(results, priority)
-    if  @category_id &&
-        priority == :high &&
-        non_category_index = @results.index{|r| r.category_id != @category_id}
+    if  @category_id && priority == :high
 
-      category_results, non_category_results = results.partition{|r| r.category_id == @category_id}
+      # Topics from category @category_id need to be first in the list, all others after.
 
-      @results.insert non_category_index, *category_results
-      @results.concat non_category_results
+      other_category_index = @results.index { |r| r.category_id != @category_id }
+      category_results, other_category_results = results.partition{ |r| r.category_id == @category_id }
+
+      if other_category_index
+        @results.insert other_category_index, *category_results
+      else
+        @results.concat category_results
+      end
+      @results.concat other_category_results
     else
       @results.concat results
     end

spec/components/suggested_topics_builder_spec.rb

@@ -37,6 +37,11 @@ describe SuggestedTopicsBuilder do
 
       builder.results.map(&:id).should == [2,3]
     end
+
+    it "inserts multiple results and puts topics in the correct order" do
+      builder.splice_results([fake_topic(2,1), fake_topic(3,2), fake_topic(4,1)], :high)
+      builder.results.map(&:id).should == [2,4,3]
+    end
   end
 
   it "has the correct defaults" do