I am using Jacoco to check the coverage of my test, i tried lots of way but it still warning 1 of 4 branches missed
fun countingDeleteDemo() : Int {
return list.count { it.isDeleted() }
}
How can I know what branch is missed? I have read some posts about the logic true && false, but is there any documents or official link about the mistake of the coverage tools?
Jacoco checks the code coverage on byte code and not on source code. As far as I know Jacoco does not show which branch is missing.
If you use IntelliJ IDEA, you can check the kotlin bytecode.
Here, the missing branch in my IDE.
// ... omitted
INVOKESTATIC kotlin/collections/CollectionsKt.throwCountOverflow ()V
// ... omitted
Kotlin's has many builtin extension function count for Iterable, Array ...
I presume that your list is a simple List, so an Iterable.
You do not have much more elements than Int.MAX_VALUE which will make the count negative.
But one can pass an iterable which may have beyond Int.MAX_VALUE elements to count.
As a good citizen, the kotlin jvm implementation checks count overflow.
You can check out the implementation details.
public inline fun <T> Iterable<T>.count(predicate: (T) -> Boolean): Int {
if (this is Collection && isEmpty()) return 0
var count = 0
for (element in this) if (predicate(element)) checkCountOverflow(++count)
return count
}
@PublishedApi
@SinceKotlin("1.3")
@InlineOnly
internal actual inline fun checkCountOverflow(count: Int): Int {
if (count < 0) {
if (apiVersionIsAtLeast(1, 3, 0))
throwCountOverflow()
else
throw ArithmeticException("Count overflow has happened.")
}
return count
}
