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Version: 5.3

Reflective Arbs

When running tests on JVM, Kotest supports generating more complex Arbs automatically. This can be useful when you have a data class which carries a simple combination of data which can already be automatically derived.


enum class Currency {

data class CurrencyAmount(
val amount: Long,
val currency: Currency

context("All currencies converts to EUR") { // In some spec
checkAll(Arb.bind<CurrencyAmount>()) { currencyAmount ->
val converted = currencyAmount.convertTo(EUR)
converted.currency shouldBe EUR

Reflective binding is supported for:

  • Data classes, where all properties also fall into this category
  • Pair, where 1st and 2nd fall into this category
  • Primitives
  • Enums
  • LocalDate, LocalDateTime, LocalTime, Period, Instant from java.time
  • BigDecimal, BigInteger
  • Collections (Set, List, Map)
  • Other types for which you have provided an Arb explicitly using the providedArbs parameter