@0x/contracts-integrations Created the FunctionAssertion class and examples

contracts/integrations/contracts/test/TestCache.sol

@@ -0,0 +1,45 @@
+pragma solidity ^0.5.9;
+
+
+contract TestCache {
+
+    uint256 public counter;
+
+    function setCounter(uint256 newCounter)
+        external
+    {
+        counter = newCounter;
+    }
+
+    function numberSideEffect()
+        external
+        view
+        returns (uint256)
+    {
+        return counter;
+    }
+
+    function equalsSideEffect(uint256 possiblyZero)
+        external
+        view
+        returns (bool)
+    {
+        if (counter == 0) {
+            return possiblyZero == 0;
+        } else {
+            return false;
+        }
+    }
+
+    function hashSideEffect(uint256 arg1, bytes32 arg2)
+        external
+        view
+        returns (bytes32)
+    {
+        if (counter == 0) {
+            return keccak256(abi.encode(arg1, arg2));
+        } else {
+            return keccak256(hex"");
+        }
+    }
+}