GUI test case migration is the process of migrating GUI test cases from a source app to a target app for a specific functionality. However, test cases obtained via existing migration approaches can hardly be directly used to test target functionalities and typically require additional manual modifications. This problem may significantly impact the effectiveness of testing target functionalities and the practical applicability of migration approaches.

In this paper, we propose \emph{MigratePro}, the first approach to enhancing GUI test case migration via \textbf{synthesizing a new test case based on multiple test cases for the same functionality} migrated from various source apps to the target app. The aim of MigratePro is to produce functional test cases with less human intervention. Specifically, given multiple migrated test cases for the same functionality in the target app, MigratePro first combines all the GUI states related to these migrated test cases into an overall state-sequence. Then, MigratePro organizes events and assertions from migrated test cases according to the overall state-sequence and endeavors to remove the should-be-removed events and assertions, while also incorporating some connection events in order to make the should-be-included events and assertions executable. Our evaluation on 30 apps, 34 functionalities, and 127 test cases shows that MigratePro improves the capability of three representative migration approaches (i.e., Craftdroid, AppFlow, ATM), successfully improving testing the target functionalities by 86%, 333%, and 300%, respectively. These results underscore the generalizability of MigratePro in effectively enhancing migration approaches.