kotlin maker example for testing

KotlinGenericMaker

## Make function (create in test directory)

inline fun <reified T> make(): T {
    return makeInstanceOfClass(T::class) as T
}

fun makeInstanceOfClass(clazz: KClass<*>): Any? {
    val primitive = makePrimitiveOrNull(clazz)
    if (primitive != null) {
        return primitive
    }

    val constructors = clazz.constructors
        .sortedBy { it.parameters.size }

    for (constructor in constructors) {
        val arguments = constructor.parameters
            .map { param ->
                param.takeUnless { it.type.isMarkedNullable }
                    ?.let { makeInstanceOfClass(it.type.classifier as KClass<*>) }
            }
            .toTypedArray()

        try {
            return constructor.call(*arguments)
        } catch (e: Throwable) {
        }
    }

    throw NoUsableConstructor(clazz)
}

private fun makePrimitiveOrNull(clazz: KClass<*>): Any? = when (clazz) {
    Int::class -> 0
    Long::class -> 0L
    Double::class -> 0.0
    String::class -> ""
    Boolean::class -> false
    UUID::class -> UUID.randomUUID()
    List::class -> emptyList<Any>()
    Set::class -> emptySet<Any>()
    Map::class -> emptyMap<Any, Any>()
    LocalDate::class -> LocalDate.now()
    LocalDateTime::class -> LocalDateTime.now()

    TrackingAction::class -> TrackingAction.CLEAN_CLICKED
    else -> null
}

class NoUsableConstructor(clazz: KClass<*>) : Error("Could not find a constructor for class: ${clazz.simpleName}")

-------------------------- Example
## Entity

data class User(
    val id: UUID,
    val firstName: String,
    val lastName: String,
    val email: String,
    val active: Boolean
)

## Initialize an entity with "primative" values

val user = make<User>()

Creates:
User(
  id = <random UUID>,
  firstName = "",
  lastName = "",
  email = "",
  active = false
)

## Initialize an entity with specfic values
-- you can set as many properties as you'd like (Tip: set only what you're testing!)

val user = make<User>().copy(firstName = "Michelle")

Creates:
User(
  id = <random UUID>,
  firstName = "Michelle",
  lastName = "",
  email = "",
  active = false
)