Kofixture is a Kotlin fixture library for tests. It gives you a small registry-based DSL for generating realistic objects, overriding only the fields that matter, and composing reusable fixture modules without reflection-heavy setup code in every test.

dependencies {
    testImplementation("io.github.kofixture:kofixture-core:0.2.3")
}

Add Kotest integration only if you want Kotest spec helpers or Arb support:

dependencies {
    testImplementation("io.github.kofixture:kofixture-kotest:0.2.3")

    testImplementation("io.kotest:kotest-runner-junit5:6.1.6")
}

Use buildRegistry {} when you want fixtures without pulling in Kotest:

import io.kofixture.Generator
import io.kofixture.buildRegistry

data class EmailAddress(val value: String)
data class User(val email: EmailAddress, val age: Int)

val registry =
    buildRegistry {
        register<EmailAddress>(Generator { EmailAddress("john@example.com") })
    }

val user = registry.next<User>()
val adult = registry.next<User> {
    override(User::age) with 42
}

What you get out of the box:

• Primitive generators for String, numbers, Boolean, UUID, Locale, ZoneId, and Instant
• Reflection-based generation for data classes and constructor-backed types
• Collection generation for List, Set, and Map
• Scoped type overrides and property overrides
• Reusable fixtureModule {} blocks

With kofixture-kotest, you can use the same registry API plus Kotest spec helpers and Arb integration:

import io.kofixture.Generator
import io.kofixture.KofixtureStringSpec
import io.kotest.property.Arb
import io.kotest.matchers.shouldBe

data class SignupRequest(val email: String, val password: String)

private val authFixtures =
    fixtureModule {
        register<String> { Arb.string(minSize = 12, maxSize = 24) }
        register<SignupRequest> {
            Generator {
                SignupRequest(
                    email = "tester@example.com",
                    password = "correct-horse-battery-staple",
                )
            }
        }
    }

class SignupRequestTest : KofixtureStringSpec() {
    override val fixtureModules = listOf(authFixtures)

    init {
        "supports property overrides" {
            val request = next<SignupRequest> {
                override(SignupRequest::email) with "invalid"
            }

            request.email shouldBe "invalid"
        }
    }
}

kofixture-kotest also adds:

• Registry.arb<T>()
• Generator<T>.toArb()
• Arb<T>.toGenerator()
• register { Arb<T> } in buildRegistry {} and fixtureModule {}
• Kotest-backed primitive overrides for Kofixture*Spec users

The repository ships with runnable examples in examples/:

• examples/core-only shows manual registry usage with kofixture-core
• examples/kotest shows KofixtureStringSpec, fixture modules, and Arb registration

Both examples use a composite build, so they exercise the local sources directly instead of relying on a published version.

• Core usage
• Kotest integration
• Fixture modules and overrides

Kofixture v2 is intentionally smaller than the old KSP-based design:

• no generated fixture registries
• no annotation processor
• one explicit registry model
• optional Kotest integration layered on top of a clean core

That keeps the library easier to understand, easier to debug, and easier to extend.