  Web end-to-end (e2e) testing evaluates the workflow of a web application. It
simulates real-world user scenarios to ensure the application flows behave as
expected. However, web e2e tests are notorious for being flaky, i.e., the tests
can produce inconsistent results despite no changes to the code. One common
type of flakiness is caused by nondeterministic execution orders between the
test code and the client-side code under test. In particular, UI-based
flakiness emerges as a notably prevalent and challenging issue to fix because
the test code has limited knowledge about the client-side code execution. In
this paper, we propose WEFix, a technique that can automatically generate fix
code for UI-based flakiness in web e2e testing. The core of our approach is to
leverage browser UI changes to predict the client-side code execution and
generate proper wait oracles. We evaluate the effectiveness and efficiency of
WEFix against 122 web e2e flaky tests from seven popular real-world projects.
Our results show that WEFix dramatically reduces the overhead (from 3.7$\times$
to 1.25$\times$) while achieving a high correctness (98%).
