Add registry tests

lib/makeup_js/application.ex

@@ -5,7 +5,7 @@ defmodule MakeupJs.Application do
   alias Makeup.Registry
 
   def start(_type, _args) do
-    Registry.register_lexer(MakeupJs,
+    Registry.register_lexer(Makeup.Lexers.JsLexer,
       options: [],
       names: ["js", "javascript"],
       extensions: ["js"]

test/registry_test.exs

@@ -0,0 +1,17 @@
+defmodule Makeup.Lexers.JsLexer.RegistryTest do
+  use ExUnit.Case, async: true
+
+  alias Makeup.Registry
+  alias Makeup.Lexers.JsLexer
+
+  describe "the Js lexer has successfully registered itself:" do
+    test "language name" do
+      assert {:ok, {JsLexer, []}} == Registry.fetch_lexer_by_name("js")
+      assert {:ok, {JsLexer, []}} == Registry.fetch_lexer_by_name("javascript")
+    end
+
+    test "file extension" do
+      assert {:ok, {JsLexer, []}} == Registry.fetch_lexer_by_extension("js")
+    end
+  end
+end