Bug fixes And add Unit Test

contracts/HelloEthSalon.sol

@@ -3,11 +3,16 @@ pragma solidity ^0.4.4;
 contract HelloEthSalon {
     string message = "I know smart contract testing!!";
 
-    function HelloEthSalon() {
+    function HelloEthSalon() public {
         // constructor
     }
 
-    function GetMessage() returns (string) {
+    function SetMessage(string m) public {
+        require(bytes(m).length > 0);
+        message = m;
+    }
+
+    function GetMessage() public returns (string) {
         return message;
     }
 }