add PHPUnit Test

Author: wujunze

composer.json

@@ -12,10 +12,18 @@
     "minimum-stability": "dev",
     "require": {
         "php": ">=5.6.0"
-    }, 
+    },
+    "require-dev":{
+        "phpunit/phpunit": "^5.0"
+    },
     "autoload": {
         "psr-4": {
             "Wujunze\\": "src" 
         }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "Wujunze\\Tests\\": "tests/"
+        }
     }
 }