Nowadays, Apple iOS and Android are two of the most popular platforms for mobile applications. To attract more users, many software companies and organizations are migrating their applications from one platform to the other, and besides source files, they need to migrate their GUI tests. The migration of GUI tests is tedious and difficult to be automated, since two platforms have subtle differences and there are often few or even no migrated GUI tests for learning. To handle the problem, in this paper, we propose a novel approach, TestMig, that migrates GUI tests from iOS to Android, without any migrated code samples. Specifically, TestMig first executes the GUI tests of the iOS version, and records their GUI event sequences. Guided by the iOS GUI events, TestMig explores the Android version of the application to generate the corresponding Android event sequences. We conducted an evaluation on five well known mobile applications: 2048, SimpleNote, Wire, Wikipedia, and WordPress. The results show that averagely TestMig correctly converts 80.2% of recorded iOS UI events to Android UI events and have them successfully executed. In addition, averagely our migrated Android test cases achieve similar statement coverage compared with the original iOS test cases (59.7% vs 60.4%).