Cross-platform app development has achieved meaningful results in practice with frameworks like React Native, Xamarin, and Apache Cordova. Unlike native apps, such frameworks support the development of a mobile app that can run in different platforms. Nevertheless, the literature lacks techniques to test cross-platform apps since most of the existing works focus on native Android apps. A promising strategy for native apps is to amplify test suites so that the specific characteristics of mobile apps can be tested. This paper aims to investigate the test amplification of cross-platform apps. To do so, we apply four test patterns that verify well-known characteristics of mobile computing and amplify existing test suites. The proposed approach has been implemented in a tool capable of generating Appium test scripts and was evaluated with nine cross-platform apps. The amplified test suites exercise new scenarios, uncovering 23 unique bugs in eight out of nine apps.