1 files changed, 14 insertions, 0 deletions
diff --git a/test/ruby/test_env.rb b/test/ruby/test_env.rb
index b14ea22996..17323ccf95 100644
--- a/test/ruby/test_env.rb
+++ b/test/ruby/test_env.rb
@@ -455,6 +455,20 @@ class TestEnv < Test::Unit::TestCase
     end
   end
 
+  def test_shared_substring
+    bug12475 = '[ruby-dev:49655] [Bug #12475]'
+    n = [*"0".."9"].join("")*3
+    e0 = ENV[n0 = "E#{n}"]
+    e1 = ENV[n1 = "E#{n}."]
+    ENV[n0] = nil
+    ENV[n1] = nil
+    ENV[n1.chop] = "T#{n}.".chop
+    ENV[n0], e0 = e0, ENV[n0]
+    ENV[n1], e1 = e1, ENV[n1]
+    assert_equal("T#{n}", e0, bug12475)
+    assert_nil(e1, bug12475)
+  end
+
   if RUBY_PLATFORM =~ /bccwin|mswin|mingw/
     def test_memory_leak_aset
       bug9977 = '[ruby-dev:48323] [Bug #9977]'