I'm using kotlinx-kover for code coverage in a project. I am using interfaces to maximize code reuse. I'm seeing something strange in one of my projects. I have the following interfaces that add convenient members (LogicGate is another interface)

interface SingleOutput: LogicGate {
    val output: Pin
        get() = outputs.first()
}
interface SingleInput: LogicGate {
    var input
        get() = inputs.first()
        set(value) { inputs[0] = value }
}

I generally implement Input first, then Output, but when I do that, kover shows that the line that says

interface SingleOutput: LogicGate

is not run. I had to switch the order of imports for one of my classes in order for the line to show as Green in kover's report. Is this expected, or a bug in kover?

This is crazy and totally believable based on my considerable experience with Jacoco, the worst but only Java class based code coverage tool I am aware of. If only someone would build a source based (preferably FOSS) tool instead of an IR based tool. I tried exactly that using Language Server Protocol before I gave up, deciding LSP was not ready for prime time for this particular task. My next effort will be with a Kotlin compiler plugin … as soon as I find funding. 🙂 (edited)

Please don't send answers to the channel, it spams everyone.

Output, but when I do that, kover shows that the line that says

interface SingleOutput: LogicGate

is not run

That’s likely to be a bug in an underlying coverage engine. Would be nice you you could report it with a reproducer to Kover GH

I can try to reproduce this and send a reproducer. From what I remember, it looked like the 'solution' of swapping order worked because it would only count coverage for the first interface.

That’s definitely something fishy; our coverage engine likely to misattribute something. It would be much appreciated!

This was over a year ago, so no promises this is still an issue. I haven't tried to undo the workaround yet and see if it still happens.