refactor(isValid): Adds getter to access isValid attribute

Author: rashidsp

Diff for: src/Optimizely/Optimizely.php

@@ -771,6 +771,14 @@ public function getFeatureVariableString($featureFlagKey, $variableKey, $userId,
         return $variableValue;
     }
 
+    /**
+     * @return boolean Flag denoting if Optimizely Instance is valid.
+     */
+    public function isValid()
+    {
+        return $this->_isValid;
+    }
+
     /**
     * Calls Validator::validateNonEmptyString for each value in array
     * Logs for each invalid value

Diff for: tests/OptimizelyTest.php

@@ -74,6 +74,18 @@ public function setUp()
             ->getMock();
     }
 
+    public function testIsValidForInvalidOptimizelyObject()
+    {
+        $optlyObject = new Optimizely('Random datafile');
+        $this->assertFalse($optlyObject->isValid());
+    }
+
+    public function testIsValidForValidOptimizelyObject()
+    {
+        $optlyObject = new Optimizely($this->datafile);
+        $this->assertTrue($optlyObject->isValid());
+    }
+
     public function testInitValidEventDispatcher()
     {
         $validDispatcher = new ValidEventDispatcher();