Allow configuring zero delay

lib/Echidna/Transaction.hs

@@ -89,7 +89,7 @@ genTx world deployedContracts = do
 genDelay :: MonadRandom m => W256 -> Set W256 -> m W256
 genDelay mv ds =
   join $ oftenUsually fromDict randValue
-  where randValue = fromIntegral <$> getRandomR (1 :: Integer, fromIntegral mv)
+  where randValue = fromIntegral <$> getRandomR (0 :: Integer, fromIntegral mv)
         fromDict = (`mod` (mv + 1)) <$> rElem' ds
 
 genValue

src/test/Tests/Integration.hs

@@ -70,6 +70,9 @@ integrationTests = testGroup "Solidity Integration Testing"
   , testContract "basic/delay.sol"        Nothing
       [ ("echidna_block_number passed",            solved    "echidna_block_number")
       , ("echidna_timestamp passed",               solved    "echidna_timestamp") ]
+  , testContract "basic/no-delay.sol"   (Just "basic/no-delay.yaml")
+      [ ("echidna_block_number failed",            passed    "echidna_block_number")
+      , ("echidna_timestamp failed",               passed    "echidna_timestamp") ]
   , testContractV "basic/immutable.sol"    (Just (>= solcV (0,6,0))) Nothing
       [ ("echidna_test passed",                    solved      "echidna_test") ]
   , testContractV "basic/immutable-2.sol"    (Just (>= solcV (0,6,0))) Nothing

tests/solidity/basic/no-delay.sol

@@ -0,0 +1,31 @@
+contract C {
+  uint blockA;
+  uint timeA;
+  uint blockB;
+  uint timeB;
+
+  constructor() public {
+    blockA = block.number;
+    timeA = block.timestamp;
+    blockB = block.number;
+    timeB = block.timestamp;
+  }
+
+  function f() public {
+    blockA = block.number;
+    timeA = block.timestamp;
+  }
+
+  function g() public {
+    blockB = block.number;
+    timeB = block.timestamp;
+  }
+
+  function echidna_block_number() public returns (bool) {
+    return blockA == blockB;
+  }
+
+  function echidna_timestamp() public returns (bool) {
+    return timeA == timeB;
+  }
+}

tests/solidity/basic/no-delay.yaml

@@ -0,0 +1,2 @@
+maxTimeDelay: 0
+maxBlockDelay: 0