Declarative Gen<T> DSL for property-based data generation, deterministic tape replay, simple shrinking/minimization, generated function values via CoGen, and low-level tape/bit utilities for deterministic testing.
kotlin-random-gen is a Kotlin Multiplatform property-based data generation library built on
kotlin-random.
It provides a declarative Gen<T> DSL, deterministic tape replay, simple shrinking/minimization for
failing values, generated function values through CoGen, and low-level bit utilities used by the
replay engine.
repositories {
mavenCentral()
}
dependencies {
implementation("one.wabbit:kotlin-random-gen:2.0.0")
}
import one.wabbit.random.gen.Gen
val userId = Gen.int(1..10_000)
val username = Gen.string(3..12, Gen.printableAsciiChar)
val user = Gen.zip(userId, username).map { (id, name) -> id to name }
Gen.foreach(user, count = 100) { (id, name) ->
check(id > 0)
check(name.isNotEmpty())
}
import kotlin.random.Random
import one.wabbit.random.gen.Gen
import one.wabbit.random.gen.sample
val value = Gen.int(0..99).sample(Random(1234))
check(value != null && value in 0..99)
sample can return null when a generator rejects a value through filter. Use sampleUnbounded
when you want to retry until a value is produced.
The sampling interpreter reads bits from a TapeSeed. Failed property checks can be minimized and
reported with the minimized tape:
import kotlin.random.Random
import one.wabbit.random.gen.Gen
import one.wabbit.random.gen.foreachMin
Gen.int(0..100).foreachMin(
random = Random(1),
iters = 100,
) { value ->
check(value < 50)
}
When minimization succeeds, MinimizedException carries the original exception, minimized value,
and replay tape.
This library is useful for internal property tests and deterministic generation workflows. The
high-level Gen APIs are the primary surface. Lower-level tape, codec, and bit-sequence utilities
are public support APIs but should be treated as advanced tools.
Generated API docs can be built locally with Dokka. See API reference notes for the command.
This project is licensed under the GNU Affero General Public License v3.0 (AGPL-3.0) for open source use.
For commercial use, contact Wabbit Consulting Corporation at wabbit@wabbit.one.
Before contributions can be merged, contributors need to agree to the repository CLA.
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