--- /dev/null
+# frozen_string_literal: true
+
+# Redmine - project management software
+# Copyright (C) 2006-2017 Jean-Philippe Lang
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+
+require File.expand_path('../../../../../test_helper', __FILE__)
+
+class Redmine::SyntaxHighlighting::RougeTest < ActiveSupport::TestCase
+ def test_highlight_by_filename_should_distinguish_perl_and_prolog
+ raw_perl = <<'RAW_PERL'
+#!/usr/bin/perl
+print "Hello, world!\n";
+RAW_PERL
+ expected_perl = <<'EXPECTED_PERL'
+<span class="c1">#!/usr/bin/perl</span>
+<span class="k">print</span> <span class="s">"Hello, world!\n"</span><span class="p">;</span>
+EXPECTED_PERL
+ raw_prolog = <<'RAW_PROLOG'
+#!/usr/bin/swipl
+:- writeln('Hello, world!'),halt.
+RAW_PROLOG
+ expected_prolog = <<'EXPECTED_PROLOG'
+<span class="c1">#!/usr/bin/swipl</span>
+<span class="p">:-</span> <span class="ss">writeln</span><span class="p">(</span><span class="ss">'Hello, world!'</span><span class="p">),</span><span class="ss">halt</span><span class="p">.</span>
+EXPECTED_PROLOG
+
+ filename = 'hello.pl'
+
+ # Rouge cannot distinguish between Perl and Prolog by filename alone
+ assert_raises Rouge::Guesser::Ambiguous do
+ Rouge::Lexer.guess(:filename => filename)
+ end
+ assert_equal Rouge::Lexers::Perl, Rouge::Lexer.guess(:filename => filename, :source => raw_perl)
+ assert_equal Rouge::Lexers::Prolog, Rouge::Lexer.guess(:filename => filename, :source => raw_prolog)
+
+ assert_equal expected_perl, Redmine::SyntaxHighlighting::Rouge.highlight_by_filename(raw_perl, filename)
+ assert_equal expected_prolog, Redmine::SyntaxHighlighting::Rouge.highlight_by_filename(raw_prolog, filename)
+ end
+end