This simple example project contains a few UI tests that highlight a bug in Android Studio's debugger.
The file MainActivityTestJava.java contains two Espresso tests, breakpointWorks() and breakpointDoesNotWork().
Adding a breakpoint at the designated lines (23 and 29, respectively) and running each test in Debug mode highlights the problem.
In breakpointWorks(), the app will successfully pause when it reaches the breakpoint on line 23.
However, in breakpointDoesNotWork(), the app will not pause if you set a breakpoint on line 29 - the only difference between this test and breakpointWorks() being the extra newlines.
Additionally, I created versions of both of these tests in Kotlin: MainActivityTest.kt. Interestingly, setting a breakpoint on the correct lines (21 and 27) pauses the app correctly in both tests, even with the extra newlines.
I reproduced this issue in Android Studio 3.4 on Mac OS 10.14.4 with the UI tests run on both a physical device (Nexus 5X running Android 8.1) and an emulator (Pixel 2 API 28).