diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -4,6 +4,12 @@
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to the [Haskell Package Versioning Policy](https://pvp.haskell.org/).
 
+## [0.4.10] - 2018-05-03
+### Added
+- Property tests for `mconcat`, `sconcat`, and `stimes`. It isn't
+  common to override the defaults for these, but when you do, it's
+  nice to check that they agree with what they are supposed to do.
+
 ## [0.4.9] - 2018-04-06
 ### Change
 - Be more careful with import of `Data.Primitive`. There is a
diff --git a/quickcheck-classes.cabal b/quickcheck-classes.cabal
--- a/quickcheck-classes.cabal
+++ b/quickcheck-classes.cabal
@@ -1,5 +1,5 @@
 name: quickcheck-classes
-version: 0.4.9
+version: 0.4.10
 synopsis: QuickCheck common typeclasses
 description:
   This library provides quickcheck properties to ensure
diff --git a/src/Test/QuickCheck/Classes/Common.hs b/src/Test/QuickCheck/Classes/Common.hs
--- a/src/Test/QuickCheck/Classes/Common.hs
+++ b/src/Test/QuickCheck/Classes/Common.hs
@@ -76,7 +76,16 @@
     -- ^ Pairs of law name and property
   }
 
-myForAllShrink :: (Arbitrary a, Show b, Eq b) => Bool -> (a -> Bool) -> (a -> [String]) -> String -> (a -> b) -> String -> (a -> b) -> Property
+myForAllShrink :: (Arbitrary a, Show b, Eq b)
+  => Bool -- Should we show the RHS. It's better not to show it
+          -- if the RHS is equal to the input.
+  -> (a -> Bool) -- is the value a valid input
+  -> (a -> [String])
+  -> String
+  -> (a -> b)
+  -> String
+  -> (a -> b)
+  -> Property
 myForAllShrink displayRhs isValid showInputs name1 calc1 name2 calc2 =
   again $
   MkProperty $
diff --git a/src/Test/QuickCheck/Classes/Monoid.hs b/src/Test/QuickCheck/Classes/Monoid.hs
--- a/src/Test/QuickCheck/Classes/Monoid.hs
+++ b/src/Test/QuickCheck/Classes/Monoid.hs
@@ -22,11 +22,14 @@
 --   @mappend mempty a ≡ a@
 -- [/Right Identity/]
 --   @mappend a mempty ≡ a@
+-- [/Concatenation/]
+--   @mconcat as ≡ foldr mappend mempty as@
 monoidLaws :: (Monoid a, Eq a, Arbitrary a, Show a) => Proxy a -> Laws
 monoidLaws p = Laws "Monoid"
   [ ("Associative", monoidAssociative p)
   , ("Left Identity", monoidLeftIdentity p)
   , ("Right Identity", monoidRightIdentity p)
+  , ("Concatenation", monoidConcatenation p)
   ]
 
 -- | Tests everything from 'monoidProps' plus the following:
@@ -37,6 +40,14 @@
 commutativeMonoidLaws p = Laws "Commutative Monoid" $ lawsProperties (monoidLaws p) ++
   [ ("Commutative", monoidCommutative p)
   ]
+
+monoidConcatenation :: forall a. (Monoid a, Eq a, Arbitrary a, Show a) => Proxy a -> Property
+monoidConcatenation _ = myForAllShrink True (const True)
+  (\(as :: [a]) -> ["as = " ++ show as])
+  "mconcat as"
+  (\as -> mconcat as)
+  "foldr mappend mempty as"
+  (\as -> foldr mappend mempty as)
 
 monoidAssociative :: forall a. (Monoid a, Eq a, Arbitrary a, Show a) => Proxy a -> Property
 monoidAssociative _ = myForAllShrink True (const True)
diff --git a/src/Test/QuickCheck/Classes/Semigroup.hs b/src/Test/QuickCheck/Classes/Semigroup.hs
--- a/src/Test/QuickCheck/Classes/Semigroup.hs
+++ b/src/Test/QuickCheck/Classes/Semigroup.hs
@@ -6,22 +6,48 @@
   ( semigroupLaws
   ) where
 
+import Prelude hiding (foldr1)
 import Data.Semigroup (Semigroup(..))
 import Data.Proxy (Proxy)
 import Test.QuickCheck hiding ((.&.))
 import Test.QuickCheck.Property (Property)
 
-import Test.QuickCheck.Classes.Common (Laws(..))
+import Test.QuickCheck.Classes.Common (Laws(..), myForAllShrink)
 
+import Data.Foldable (foldr1,toList)
+import Data.List.NonEmpty (NonEmpty((:|)))
+
 -- | Tests the following properties:
 --
 -- [/Associative/]
 --   @a <> (b <> c) ≡ (a <> b) <> c@
+-- [/Concatenation/]
+--   @sconcat as ≡ foldr1 (<>) as@
+-- [/Times/]
+--   @stimes n a ≡ foldr1 (<>) (replicate n a)@
 semigroupLaws :: (Semigroup a, Eq a, Arbitrary a, Show a) => Proxy a -> Laws
 semigroupLaws p = Laws "Semigroup"
   [ ("Associative", semigroupAssociative p)
+  , ("Concatenation", semigroupConcatenation p)
+  , ("Times", semigroupTimes p)
   ]
 
 semigroupAssociative :: forall a. (Semigroup a, Eq a, Arbitrary a, Show a) => Proxy a -> Property
 semigroupAssociative _ = property $ \(a :: a) b c -> a <> (b <> c) == (a <> b) <> c
+
+semigroupConcatenation :: forall a. (Semigroup a, Eq a, Arbitrary a, Show a) => Proxy a -> Property
+semigroupConcatenation _ = myForAllShrink True (const True)
+  (\(a, as :: [a]) -> ["as = " ++ show (a :| as)])
+  "sconcat as"
+  (\(a,as) -> sconcat (a :| as))
+  "foldr1 (<>) as"
+  (\(a,as) -> foldr1 (<>) (a :| as))
+
+semigroupTimes :: forall a. (Semigroup a, Eq a, Arbitrary a, Show a) => Proxy a -> Property
+semigroupTimes _ = myForAllShrink True (\(_,n) -> n > 0)
+  (\(a :: a, n :: Int) -> ["a = " ++ show a, "n = " ++ show n])
+  "stimes n a"
+  (\(a,n) -> stimes n a)
+  "foldr1 (<>) (replicate n a)"
+  (\(a,n) -> foldr1 (<>) (replicate n a))
 
diff --git a/test/Spec.hs b/test/Spec.hs
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -71,6 +71,7 @@
 allLaws p = 
   [ primLaws p
   , storableLaws p
+  , semigroupLaws (Proxy :: Proxy (Sum a))
   , monoidLaws (Proxy :: Proxy (Sum a))
   , showReadLaws p
 #if defined(VERSION_aeson)