Unit test for fix #1809 on heuristics

test/test_heuristics.rb

@@ -20,6 +20,11 @@ class TestHeuristcs < Test::Unit::TestCase
     Dir.glob("#{samples_path}/#{language_name}/#{file}")
   end
 
+  def test_no_language
+    results = Heuristics.call(file_blob("C++/render_adapter.cpp"), [])
+    assert_equal [], results
+  end
+
   # Candidate languages = ["C++", "Objective-C"]
   def test_obj_c_by_heuristics
     # Only calling out '.h' filenames as these are the ones causing issues