Improve coverage over debug page

Author: josevalim

test/plug/debugger_test.exs

@@ -330,12 +330,15 @@ defmodule Plug.DebuggerTest do
       |> put_req_header("accept", "text/html")
       |> Plug.Parsers.call(Plug.Parsers.init(parsers: [:urlencoded]))
       |> put_req_header("<script>xss-header</script>", "<script>xss-val</script>")
-      |> render([], fn -> raise "<script>oops</script>" end)
+      |> render([], fn -> raise "<script>xss-error</script>" end)
 
     assert conn.resp_body =~ "x=&lt;script&gt;alert(document.domain)&lt;/script&gt;"
     assert conn.resp_body =~ "&lt;script&gt;xss-header&lt;/script&gt;"
     assert conn.resp_body =~ "&lt;script&gt;xss-val&lt;/script&gt;"
-    assert conn.resp_body =~ "&lt;script&gt;oops&lt;/script&gt;"
+    assert conn.resp_body =~ "&lt;script&gt;xss-error&lt;/script&gt;"
+
+    refute conn.resp_body =~ "<script>alert"
+    refute conn.resp_body =~ "<script>xss"
   end
 
   test "uses PLUG_EDITOR with __FILE__" do