run AssetsManagerTest on android device, update failed

Hi~
when I run the tests on android device ,it’s failed and logcat tell me “can not create file cocos2dx-update-temp-package.zip”, from the source I know the error is " FILE *fp = fopen(outFileName.c_str(), “wb”);", fopen failed and pointer fp is null. I had gave the app permission ,but it still couldn’t work.
anyone else know it?