Use withNumTests and require QuickCheck >= 2.18.

pandoc.cabal

@@ -855,6 +855,7 @@ test-suite test-pandoc
                   tasty-golden      >= 2.3     && < 2.4,
                   tasty-hunit       >= 0.9     && < 0.11,
                   tasty-quickcheck  >= 0.8     && < 0.12,
+                  QuickCheck        >= 2.18    && < 2.19,
                   text              >= 1.1.1.0 && < 2.2,
                   temporary         >= 1.1     && < 1.4,
                   time              >= 1.5     && < 1.17,

test/Tests/Readers/HTML.hs

@@ -139,7 +139,7 @@ tests = [ testGroup "base tag"
           ]
         , askOption $ \(QuickCheckTests numtests) ->
             testProperty "Round trip" $
-              withMaxSuccess (if QuickCheckTests numtests == defaultValue
+              withNumTests (if QuickCheckTests numtests == defaultValue
                                  then 25
                                  else numtests) roundTrip
         ]