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diff --git a/testsuite/tests/simplCore/should_run/T2486.hs b/testsuite/tests/simplCore/should_run/T2486.hs
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+++ b/testsuite/tests/simplCore/should_run/T2486.hs
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+{-# OPTIONS_GHC -O -ddump-rules #-}
+
+-- Trac #2486
+--
+-- The thing to look for here is that specialisations for fib and tak 
+-- at both Int and Double are indeed generated; hence -ddump-rules
+
+module Main where
+
+import System.Environment
+import Numeric
+
+main = do
+    n <- getArgs >>= readIO . head
+    let m  = n-1
+        a  = 27 + fromIntegral n
+    putStr $
+       line "Ack" [3,n]       (ack 3 n)                     show ++
+       line "Fib" [a]         (fib a             :: Double) (\n -> showFFloat (Just 1) n []) ++
+       line "Tak" [3*m,2*m,m] (tak (3*m) (2*m) m :: Int)    show ++
+       line "Fib" [3]         (fib 3             :: Int)    show ++
+       line "Tak" [3,2,1]     (tak 3 2 1         :: Double) show
+    where
+       line pre a r f = pre ++ "(" ++ csv f a "" ++ "): " ++ f r ++ "\n"
+       csv f [a]   s  = s ++ f a
+       csv f (a:b) s  = s ++ f a ++ "," ++ csv f b s
+
+ack :: Int -> Int -> Int
+ack 0 n = n+1
+ack m 0 = ack (m-1) 1
+ack m n = ack (m-1) (ack m (n-1))
+
+fib :: (Num a, Ord a) => a -> a
+fib     n = if n >= 2 then fib  (n-1) + fib  (n-2) else 1
+
+tak :: (Num a, Ord a) => a -> a -> a -> a
+tak x y z = if y < x then tak (tak (x-1) y z) (tak (y-1) z x) (tak (z-1) x y) else z