Added makeInterfaceId tests. (#1530)

contracts/mocks/OwnableInterfaceId.sol

@@ -0,0 +1,15 @@
+pragma solidity ^0.4.24;
+
+import "../ownership/Ownable.sol";
+
+/**
+ * @title Ownable interface id calculator.
+ * @dev See the EIP165 specification for more information:
+ * https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md#specification
+ */
+contract OwnableInterfaceId {
+    function getInterfaceId() public pure returns (bytes4) {
+        Ownable i;
+        return i.owner.selector ^ i.isOwner.selector ^ i.renounceOwnership.selector ^ i.transferOwnership.selector;
+    }
+}