Arb.stringPattern slows down the test dramatically

I used to have this in my code

fun Arb.Companion.alphanumeric(): Arb<String> = Arb.stringPattern("[a-zA-Z0-9]+")

and used it everywhere. Tests became extremely slow after the upgrade to Kotest 4.3.1 (from 4.2.x). Let me know if you need more info.

A

[sksamuel]

If you make the fix Mitchell I’ll release 4.3.2

On Fri, 4 Dec 2020, 05:25 Mitchell Yuwono, [e-mail] wrote:

I think i might have found the root cause. Arb.pattern is instantiating Generex object on every sample. I managed to replicate this slowdown and confirmed that it is indeed a regression. It seems we need to cache the Generex object. I’ll raise a fix for that @sksamuel https://github.com/sksamuel

This is the arb https://github.com/kotest/kotest/blob/99138d177bd52feea19740abeec6c5c4a3ae11c1/kotest-property/src/jvmMain/kotlin/io/kotest/property/arbitrary/stringsjvm.kt#L7-L16

fun main() { val startCached = TimeSource.Monotonic.markNow() arbCachedPattern(“[a-zA-Z0-9]+”).take(10000).toList() println(“cached: ${startCached.elapsedNow()}”) // cached: 214ms

val startNotCached = TimeSource.Monotonic.markNow()
Arb.stringPattern("[a-zA-Z0-9]+").take(10000).toList()
println("not cached: ${startNotCached.elapsedNow()}")
// not cached: 2.71s

} // caching the Generex objectfun arbCachedPattern(pattern: String) = object : Arb<String>() { val generex = Generex(pattern) override fun edgecases(): List<String> = emptyList() override fun sample(rs: RandomSource): Sample<String> { generex.setSeed(rs.random.nextLong()) return sampleOf(generex.random(), StringShrinker) } }

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[sksamuel]

4.3.2 is released with this fix.