diff --git a/EasyMapping.podspec b/EasyMapping.podspec
index ab194b3..a78f9a3 100644
--- a/EasyMapping.podspec
+++ b/EasyMapping.podspec
@@ -15,12 +15,17 @@ Pod::Spec.new do |s|
 
   s.ios.deployment_target = '5.0'
   s.osx.deployment_target = '10.7'
-  s.frameworks = 'CoreData'
 
-  s.source_files = 'EasyMapping/*.{h,m}'
+  s.subspec 'Core' do |core|
+    core.frameworks = 'CoreData'
+    core.source_files = 'EasyMapping/*.{h,m}'
+  end
 
   s.subspec 'XCTest' do |xctest|
+    xctest.dependency 'EasyMapping/Core'
     xctest.frameworks = 'XCTest'
     xctest.source_files = 'XCTest+EasyMapping/*.{h,m}'
   end
+
+  s.default_subspec = 'Core'
 end
diff --git a/XCTest+EasyMapping/XCTestCase+EasyMapping.m b/XCTest+EasyMapping/XCTestCase+EasyMapping.m
index 3a72ecb..cf14a99 100644
--- a/XCTest+EasyMapping/XCTestCase+EasyMapping.m
+++ b/XCTest+EasyMapping/XCTestCase+EasyMapping.m
@@ -64,7 +64,7 @@ - (void)testMappedObject:(id)mappedObject withMapping:(EKObjectMapping *)mapping
         NSArray *relationshipKeyPathsToSkip = [self extractRelationshipKeyPathsFromKeyPaths:keyPathsToSkip forRelationship:keyPath];
         [relationshipObjects enumerateObjectsUsingBlock:^(id relationshipObject, NSUInteger idx, BOOL *stop) {
             id expectedRelationshipObject = expectedRelationshipObjects[idx];
-            NSString *indexKeyPath = [NSString stringWithFormat:@"%@[%lu]", keyPath, idx];
+            NSString *indexKeyPath = [NSString stringWithFormat:@"%@[%@]", keyPath, @(idx)];
             NSString *relationshipRootKeyPath = [self keyPathByAppendingKeyPath:indexKeyPath
                                                                   toRootKeyPath:rootKeyPath];
             [self testMappedObject:relationshipObject withMapping:hasManyMapping.objectMapping expectedObject:expectedRelationshipObject skippingKeyPaths:relationshipKeyPathsToSkip rootKeyPath:relationshipRootKeyPath];
@@ -125,7 +125,7 @@ - (void)testSerializedObject:(NSDictionary *)serializedObject withMapping:(EKObj
         NSArray *relationshipKeyPathsToSkip = [self extractRelationshipKeyPathsFromKeyPaths:keyPathsToSkip forRelationship:keyPath];
         [relationshipRepresentations enumerateObjectsUsingBlock:^(id relationshipRepresentation, NSUInteger idx, BOOL *stop) {
             id expectedRelationshipRepresentation = expectedRelationshipRepresentations[idx];
-            NSString *indexKeyPath = [NSString stringWithFormat:@"%@[%lu]", keyPath, idx];
+            NSString *indexKeyPath = [NSString stringWithFormat:@"%@[%@]", keyPath, @(idx)];
             NSString *relationshipRootKeyPath = [self keyPathByAppendingKeyPath:indexKeyPath
                                                                   toRootKeyPath:rootKeyPath];
             [self testSerializedObject:relationshipRepresentation withMapping:hasManyMapping.objectMapping expectedRepresentation:expectedRelationshipRepresentation skippingKeyPaths:relationshipKeyPathsToSkip rootKeyPath:relationshipRootKeyPath];