Add number of pieces property test

1 files changed, 16 insertions, 0 deletions

diff --git a/test/Test.hs b/test/Test.hs
index c5c694e..e07fcc5 100644
--- a/test/Test.hs
+++ b/test/Test.hs
@@ -27,6 +27,15 @@ atAnyState ok pgn = and [ok b | Right b <- seqList [moveSAN m | m <- moves pgn]
     seqList _      (Left _)   = []
     seqList []     _          = []
 
+atAnyTwoStates :: (Board -> Board -> Bool) -> PGN -> Bool
+atAnyTwoStates ok pgn = and [ok b1 b2 | Right b1 <- seqList [moveSAN m | m <- moves pgn] | Right b2 <- seqList [moveSAN m | m <- moves pgn] $ Right defaultBoard]
+  where
+    seqList :: [r -> Either e r] -> Either e r -> [Either e r]
+    seqList (f:fs) (Right io) = f io:seqList fs (f io)
+    seqList _      (Left _)   = []
+    seqList []     _          = []
+
+
 prop_checkPGN :: PGN -> Bool
 prop_checkPGN pgn
   | isLeft parsed       = False
@@ -75,5 +84,12 @@ prop_only_2_kings = atAnyState (\b ->
   where
     pieceCoords clr brd piece = [i | (i, pc) <- (assocs $ board brd), pc == Just (Piece clr piece)]
 
+prop_number_of_pieces :: PGN -> Bool
+prop_number_of_pieces = atAnyTwoStates (\b1 b2 ->
+  length (pieceCoords Nothing Nothing b1) == length (pieceCoords Nothing Nothing b2)
+  ||
+  length (pieceCoords Nothing Nothing b1) - 1 == length (pieceCoords Nothing Nothing b2)
+  )
+
 return []
 main = $forAllProperties (quickCheckWithResult (stdArgs {maxSuccess=10000}))