add route test framework

contracts/lib/ExternalCall.sol

@@ -0,0 +1,34 @@
+/*
+
+    Copyright 2020 DODO ZOO.
+    SPDX-License-Identifier: Apache-2.0
+
+*/
+
+pragma solidity 0.6.9;
+pragma experimental ABIEncoderV2;
+
+library ExternalCall {
+    // Source: https://github.com/gnosis/MultiSigWallet/blob/master/contracts/MultiSigWallet.sol
+    // call has been separated into its own function in order to take advantage
+    // of the Solidity's code generator to produce a loop that copies tx.data into memory.
+    function externalCall(address destination, uint value, bytes memory data, uint dataOffset, uint dataLength, uint gasLimit) internal returns(bool result) {
+        // solium-disable-next-line security/no-inline-assembly
+        if (gasLimit == 0) {
+            gasLimit = gasleft() - 40000;
+        }
+        assembly {
+            let x := mload(0x40)   // "Allocate" memory for output (0x40 is where "free memory" pointer is stored by convention)
+            let d := add(data, 32) // First 32 bytes are the padded length of data, so exclude that
+            result := call(
+                gasLimit,
+                destination,
+                value,
+                add(d, dataOffset),
+                dataLength,        // Size of the input (in bytes) - this is what fixes the padding problem
+                x,
+                0                  // Output is ignored, therefore the output size is zero
+            )
+        }
+    }
+}