Don't shrink the action chosen in state machine testing

hedgehog/src/Hedgehog/Internal/Gen.hs

@@ -93,6 +93,7 @@ module Hedgehog.Internal.Gen (
   -- ** Choice
   , constant
   , element
+  , element_
   , choice
   , frequency
   , recursive
@@ -1186,6 +1187,20 @@ element = \case
     n <- integral $ Range.constant 0 (length xs - 1)
     pure $ xs !! n
 
+-- | Randomly selects one of the elements in the list.
+--
+--   This generator does not shrink the choice of element.
+--
+--   /The input list must be non-empty./
+--
+element_ :: MonadGen m => [a] -> m a
+element_ = \case
+  [] ->
+    error "Hedgehog.Gen.element: used with empty list"
+  xs -> do
+    n <- integral_ $ Range.constant 0 (length xs - 1)
+    pure $ xs !! n
+
 -- | Randomly selects one of the generators in the list.
 --
 --   This generator shrinks towards the first generator in the list.

hedgehog/src/Hedgehog/Internal/State.hs

@@ -542,7 +542,7 @@ action commands =
     Context state0 _ <- get
 
     Command mgenInput exec callbacks <-
-      Gen.element $ filter (\c -> commandGenOK c state0) commands
+      Gen.element_ $ filter (\c -> commandGenOK c state0) commands
 
     input <-
       case mgenInput state0 of
@@ -579,7 +579,7 @@ genActions range commands ctx = do
 
 -- | A sequence of actions to execute.
 --
-data Sequential m state =
+newtype Sequential m state =
   Sequential {
       -- | The sequence of actions.
       sequentialActions :: [Action m state]