added test (don't know if it works yet)

src/test/Tests/Integration.hs

@@ -70,6 +70,8 @@ integrationTests = testGroup "Solidity Integration Testing"
       , ("echidna_timestamp passed",               solved    "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
+      [ ("echidna_test passed",                    solved      "echidna_test") ]
   , testContract "basic/construct.sol"    Nothing
       [ ("echidna_construct passed",               solved      "echidna_construct") ]
   , testContract "basic/gasprice.sol"     (Just "basic/gasprice.yaml")

tests/solidity/basic/immutable-2.sol

@@ -0,0 +1,15 @@
+import "./immutable-3.sol";
+
+contract C {
+  D d;
+  constructor() {
+    d = new D(0);
+  }
+  function set(uint256 n, uint256 m) external {
+    d = new D(n);
+    d.set(m);
+  }
+  function echidna_test() public returns (bool) {
+    return d.state();
+  }
+}

tests/solidity/basic/immutable-3.sol

@@ -0,0 +1,12 @@
+contract D {
+  uint256 public immutable n;
+  bool public state = true;
+  constructor(uint256 _n) {
+    n = _n;
+  }
+  function set(uint256 m) external {
+    if (n+1 != 101) revert();
+    if (m+1 != 104) revert();
+    state = false;
+  }
+}