TOSQUASH forgot to add new file

ouroboros-consensus/src/unstable-mempool-test-utils/Test/Consensus/Mempool/Multiplicity.hs

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+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE LambdaCase   #-}
+
+module Test.Consensus.Mempool.Multiplicity (leastMultiplicity) where
+
+import           Ouroboros.Consensus.Mock.Ledger.Block (simpleBlockTxCapacity)
+import           Ouroboros.Network.SizeInBytes (SizeInBytes)
+
+-- | This function accurately mimics how
+-- 'Ouroboros.Consensus.Mempool.Update.shouldTryToAddTx' would behave when
+-- adding valid transactions of the following sizes, in order, to an initially
+-- empty mempool.
+leastMultiplicity :: [SizeInBytes] -> Int
+leastMultiplicity =
+    go 1 0
+  where
+    go !n !acc = \case
+      []   -> n
+      x:xs ->
+        if acc + x <= simpleBlockTxCapacity
+        then go  n      (acc + x) xs
+        else go (n + 1)        x  xs