Add missing testcases

tests/shadowing_abstract.sol

@@ -0,0 +1,9 @@
+contract BaseContract{
+    address owner;
+
+}
+
+contract DerivedContract is BaseContract{
+    address owner;
+
+}

tests/shadowing_state_variable.sol

@@ -0,0 +1,21 @@
+contract BaseContract{
+    address owner;
+
+    modifier isOwner(){
+        require(owner == msg.sender);
+        _;
+    }
+
+}
+
+contract DerivedContract is BaseContract{
+    address owner;
+
+    constructor(){
+        owner = msg.sender;
+    }
+
+    function withdraw() isOwner() external{
+        msg.sender.transfer(this.balance);
+    }
+}