FIX: An `opts` hash was not, in fact, optional :)

lib/topic_retriever.rb

@@ -4,8 +4,8 @@ class TopicRetriever
 
   def initialize(embed_url, opts = nil)
     @embed_url = embed_url
-    @author_username = opts[:author_username]
     @opts = opts || {}
+    @author_username = @opts[:author_username]
   end
 
   def retrieve

spec/components/topic_retriever_spec.rb

@@ -8,6 +8,11 @@ describe TopicRetriever do
   let(:author_username) { "eviltrout" }
   let(:topic_retriever) { TopicRetriever.new(embed_url, author_username: author_username) }
 
+  it "can initialize without optional parameters" do
+    t = TopicRetriever.new(embed_url)
+    expect(t).to be_present
+  end
+
   describe "#retrieve" do
     context "when host is invalid" do
       before do