1 files changed, 11 insertions, 0 deletions
diff --git a/test/fiddle/test_import.rb b/test/fiddle/test_import.rb
index 99294ea161..e243105568 100644
--- a/test/fiddle/test_import.rb
+++ b/test/fiddle/test_import.rb
@@ -149,7 +149,18 @@ module Fiddle
     end
 
     def test_no_message_with_debug
+      # disable all Ruby environment variables
+      orig_RUBYOPT, ENV['RUBYOPT'] = ENV['RUBYOPT'], nil
+      orig_RUBYLIB, ENV['RUBYLIB'] = ENV['RUBYLIB'], nil
+
+      # load development fiddle instead of bundled one
+      libdir = File.expand_path('../../../lib', __FILE__)
+      ENV['RUBYLIB'] = libdir if File.file?(File.join(libdir, "fiddle/import.rb"))
+
       assert_in_out_err(%w[--debug --disable=gems -rfiddle/import], 'p Fiddle::Importer', ['Fiddle::Importer'])
+    ensure
+      ENV['RUBYLIB'] = orig_RUBYLIB
+      ENV['RUBYOPT'] = orig_RUBYOPT
     end
   end
 end if defined?(Fiddle)