Refactored mock contract

contracts/common/interfaces.sol

@@ -7,4 +7,13 @@ interface ERC20 {
     function deposit() external payable;
     function withdraw(uint) external;
     function balanceOf(address) external view returns (uint);
+}
+
+interface MemoryInterface {
+    function getUint(uint id) external returns (uint num);
+    function setUint(uint id, uint val) external;
+}
+
+interface EventInterface {
+    function emitEvent(uint connectorType, uint connectorID, bytes32 eventCode, bytes calldata eventData) external;
 }

contracts/common/stores.sol

@@ -1,13 +1,7 @@
 pragma solidity ^0.6.0;
 
-interface MemoryInterface {
+import { MemoryInterface, EventInterface} from "./interfaces.sol";
-    function getUint(uint id) external returns (uint num);
-    function setUint(uint id, uint val) external;
-}
 
-interface EventInterface {
-    function emitEvent(uint connectorType, uint connectorID, bytes32 eventCode, bytes calldata eventData) external;
-}
 
 contract Stores {
 

contracts/connectors/mock.sol

@@ -1,7 +1,7 @@
 pragma solidity ^0.6.0;
 
 // import files from common directory
-import { ERC20 } from "../common/ERC20.sol";
+import { ERC20 , MemoryInterface, EventInterface} from "../common/interfaces.sol";
 import { Stores } from "../common/stores.sol";
 import { DSMath } from "../common/math.sol";