1 files changed, 31 insertions, 2 deletions
diff --git a/test/ruby/test_rand.rb b/test/ruby/test_rand.rb
index 67b6df8562..c7139818de 100644
--- a/test/ruby/test_rand.rb
+++ b/test/ruby/test_rand.rb
@@ -415,14 +415,43 @@ END
 
   def test_fork_shuffle
     pid = fork do
-        (1..10).to_a.shuffle
-        raise 'default seed is not set' if srand == 0
+      (1..10).to_a.shuffle
+      raise 'default seed is not set' if srand == 0
     end
     p2, st = Process.waitpid2(pid)
     assert(st.success?, "#{st.inspect}")
   rescue NotImplementedError, ArgumentError
   end
 
+  def assert_fork_status(n, mesg, &block)
+    IO.pipe do |r, w|
+      (1..n).map do
+        p1 = fork {w.puts(block.call.to_s)}
+        _, st = Process.waitpid2(p1)
+        assert_send([st, :success?], mesg)
+        r.gets.strip
+      end
+    end
+  end
+
+  def test_rand_reseed_on_fork
+    bug5661 = '[ruby-core:41209]'
+
+    assert_fork_status(1, bug5661) {Random.rand(4)}
+    r1, r2 = *assert_fork_status(2, bug5661) {Random.rand}
+    assert_not_equal(r1, r2, bug5661)
+
+    assert_fork_status(1, bug5661) {rand(4)}
+    r1, r2 = *assert_fork_status(2, bug5661) {rand}
+    assert_not_equal(r1, r2, bug5661)
+
+    stable = Random.new
+    assert_fork_status(1, bug5661) {stable.rand(4)}
+    r1, r2 = *assert_fork_status(2, bug5661) {stable.rand}
+    assert_equal(r1, r2, bug5661)
+  rescue NotImplementedError
+  end
+
   def test_seed
     bug3104 = '[ruby-core:29292]'
     rand_1 = Random.new(-1).rand