Refactoring and tests

Author: alexkart

.gitignore

@@ -1,2 +1,3 @@
 /vendor/
 /examples/looker_access_token.txt
+/.phpunit.result.cache

composer.json

@@ -2,10 +2,14 @@
     "autoload": {
         "psr-4": {
             "Alexkart\\Looker\\": "src/",
-            "App\\": "examples/"
+            "App\\": "examples/",
+            "Tests\\": "tests/"
         }
     },
     "require": {
         "alexkart/looker-php-sdk": "^0.1.0"
+    },
+    "require-dev": {
+        "phpunit/phpunit": "^9.5"
     }
 }