Inline functions are causing errors in unit test code coverage report

Question

I'm writing some unit tests for my Android app written in Kotlin, and I'm getting errors from the included inlined collection functions, in this case specifically sortedBy

 override fun onDaysSelected(dayOfWeekList: ArrayList<DayOfWeek>) {
        view.userRoutingRule.days = dayOfWeekList.sortedBy { it.dayOfWeek }
        renderRule()
 }

This is the error I'm getting when I run my unit tests with coverage

---- IntelliJ IDEA coverage runner ---- sampling ... include patterns: com.mypackage..* exclude patterns:[2019.02.02 14:49:40] (Coverage): Class data was not extracted: com.mypackage\myfile$onDaysSelected$$inlined$sortedBy$1: java.lang.Throwable

Process finished with exit code 0

My unit tests all pass accordingly, but when I go to look at the coverage report, it's almost completely bare as this error stopped it from completing.

Is there any solution to this at this point? It's hard to know if I missed some condition if I can't just look at the report.

Answer 1

It's a known issue with calculating coverage of imline methods that use lambdas. (see No coverage report for inlined Kotlin methods and https://discuss.kotlinlang.org/t/inline-functions-coverage/5366)

If you want to run coverage in the current state, you'll need to use other approaches, for example implementing Comparable interface in your DayOfWeek and using .sorted() method.