tests: move test/helpers to test/test_helpers.

The Rails convention is for test/helpers to be used for testing the view
helpers in app/helpers. We were using it to store certain utility
methods instead. Move these to test/test_helpers so that test/helpers
can be used for its intended purpose.

test/test_helpers/iqdb_test_helper.rb

@@ -0,0 +1,32 @@
+module IqdbTestHelper
+  def mock_iqdb_service!
+    mock_sqs_service = Class.new do
+      def initialize
+        @commands = []
+      end
+
+      def commands
+        @commands
+      end
+
+      def send_message(msg)
+        @commands << msg.split(/\n/).first
+      end
+    end
+
+    service = mock_sqs_service.new
+    Post.stubs(:iqdb_sqs_service).returns(service)
+    Post.stubs(:iqdb_enabled?).returns(true)
+
+    Danbooru.config.stubs(:iqdbs_auth_key).returns("hunter2")
+    Danbooru.config.stubs(:iqdbs_server).returns("http://localhost:3004")
+  end
+
+  def mock_iqdb_matches!(post_or_source, matches)
+    source = post_or_source.is_a?(Post) ? post_or_source.complete_preview_file_url : post_or_source
+    url = "http://localhost:3004/similar?key=hunter2&url=#{CGI.escape source}&ref"
+    body = matches.map { |post| { post_id: post.id } }.to_json
+
+    stub_request(:get, url).to_return(body: body)
+  end
+end