isfeatureenabled should return boolean value. (#39)

Author: msohailhussain

OptimizelySDK.Tests/OptimizelyTest.cs

@@ -1391,11 +1391,11 @@ public void TestIsFeatureEnabledGivenNullOrEmptyArguments()
         {
             var featureKey = "featureKey";
 
-            Assert.Null(Optimizely.IsFeatureEnabled(featureKey, null, null));
-            Assert.Null(Optimizely.IsFeatureEnabled(featureKey, "", null));
-
-            Assert.Null(Optimizely.IsFeatureEnabled(null, TestUserId, null));
-            Assert.Null(Optimizely.IsFeatureEnabled("", TestUserId, null));
+            Assert.IsFalse(Optimizely.IsFeatureEnabled(featureKey, null, null));
+            Assert.IsFalse(Optimizely.IsFeatureEnabled(featureKey, "", null));
+                   
+            Assert.IsFalse(Optimizely.IsFeatureEnabled(null, TestUserId, null));
+            Assert.IsFalse(Optimizely.IsFeatureEnabled("", TestUserId, null));
 
             LoggerMock.Verify(l => l.Log(LogLevel.ERROR, "User ID must not be empty."), Times.Exactly(2));
             LoggerMock.Verify(l => l.Log(LogLevel.ERROR, "Feature flag key must not be empty."), Times.Exactly(2));
@@ -1406,7 +1406,7 @@ public void TestIsFeatureEnabledGivenNullOrEmptyArguments()
         public void TestIsFeatureEnabledGivenFeatureFlagNotFound()
         {
             var featureKey = "feature_not_found";
-            Assert.Null(Optimizely.IsFeatureEnabled(featureKey, TestUserId, null));
+            Assert.IsFalse(Optimizely.IsFeatureEnabled(featureKey, TestUserId, null));
 
             LoggerMock.Verify(l => l.Log(LogLevel.ERROR, $@"Feature key ""{featureKey}"" is not in datafile."));
         }

OptimizelySDK/Optimizely.cs

@@ -334,23 +334,23 @@ public Variation GetForcedVariation(string experimentKey, string userId)
         /// <param name="userId">The user ID</param>
         /// <param name="userAttributes">The user's attributes.</param>
         /// <returns>True if feature is enabled, false or null otherwise</returns>
-        public bool? IsFeatureEnabled(string featureKey, string userId, UserAttributes userAttributes = null)
+        public bool IsFeatureEnabled(string featureKey, string userId, UserAttributes userAttributes = null)
         {
             if (string.IsNullOrEmpty(userId))
             {
                 Logger.Log(LogLevel.ERROR, "User ID must not be empty.");
-                return null;
+                return false;
             }
 
             if (string.IsNullOrEmpty(featureKey))
             {
                 Logger.Log(LogLevel.ERROR, "Feature flag key must not be empty.");
-                return null;
+                return false;
             }
 
             var featureFlag = Config.GetFeatureFlagFromKey(featureKey);
             if (string.IsNullOrEmpty(featureFlag.Key))
-                return null;
+                return false;
 
             if (!Validator.IsFeatureFlagValid(Config, featureFlag))
                 return false;