fabrikate4k

fabrikate4k

A test utility to instantiate objects with fake data.

Installation

In Gradle, install the ForkHandles BOM and then this module in the dependency block:

implementation(platform("dev.forkhandles:forkhandles-bom:X.Y.Z"))
testImplementation("dev.forkhandles:fabrikate4k")

Usage

data class Hobby(val name: String)

data class Person(
    val firstName: String,
    val lastName: String,
    val age: Int,
    val hobbies: List<Hobby>,
    val birthdate: LocalDate
)

val randomPerson: Person = Fabrikate().random()

/*
Person(
    firstName=tzCNl, 
    lastName=SggkQ, 
    age=-191063271, 
    hobbies=[Hobby(name=q8IPqL)], 
    birthdate=1992-03-14
)
 */

Creating a custom Fabrikator

If you need more control over the randomly created data you can register your own implementation:

val myRandomString: Fabricator<String> = Fabricator { UUID.randomUUID().toString() }

val myRandomInt: Fabricator<Int> = Fabricator { Random.nextInt(20, 60) }

val config = FabricatorConfig()
    .register(myRandomString)
    .register(myRandomInt)

val randomPerson: Person = Fabrikate(config).random()

/*
Person(
    firstName=acd9c9cc-646e-4890-b10d-03ada70b4ab7,
    lastName=7d31d77a-f9f8-4b6d-95df-8602a777e360, 
    age=39, 
    birthdate=2006-05-12,
    hobbies=[
        Hobby(name=7f2a55ec-ad0a-45a1-9a98-8b0d568f24ba), 
        Hobby(name=a34120ed-210e-4433-b2c1-5fa0692777f6), 
        Hobby(name=b132758e-cc2c-4df1-8479-bda6aae33e45), 
        Hobby(name=910813a3-3026-4e45-b5d6-253204e47eea), 
        Hobby(name=8b8f1b3e-e629-4603-8b93-2b8a1f3e1c4d)
    ]
)
 */

A fabricator can use the instance of Fabrikate if needed :

interface Person {
    val name: String
}

data class Parent(
    override val name: String,
    val children: List<Person>,
) : Person

data class Child(
    override val name: String,
) : Person

val myRandomParent: Fabricator<Parent> = Fabricator {
    Parent(it.random(), it.random<List<Child>>())
}

val myRandomPerson: Fabricator<Person> = Fabricator {
    if (!it.config.random.nextBoolean()) it.random<Parent>()
    else it.random<Child>()
}

val config = FabricatorConfig()
    .register(StringFabricator())
    .register(myRandomParent)
    .register(myRandomPerson)

val randomPerson: Person = Fabrikate(config).random()

/*
Parent(
    name=DAel,
    children=[
        Child(name=P56I7)
    ]
)
*/

Configuring the fabrication

FabrikatorConfig can be configured by passing parameters to adjust the behavior during fabrication.

Parameter	Description
seed	An Int used as a seed to the random number generator. This is useful if you want to control creation, e.g. in tests.
nullableStrategy	A NullableStrategy that will prevent the creation of null values for nullable types when set to NeverSetToNull, or always creates null values for nullable types when set to AlwaysSetToNull. Defaults to RandomlySetToNull.
collectionSizes	An IntRange that defines the number of elements to create when fabricating collections. Defaults to 1..5.

If you want to call a fabricator as a standalone :

val myRandomString: Fabricator<String> = Fabricator { UUID.randomUUID().toString() }

myRandomString()

You can also configure it :

val myRandomString: Fabricator<String> = Fabricator { UUID.randomUUID().toString() }

val randomPerson = Fabrikate().random<Person> { config ->
    config.withMapping(myRandomString)
}

It is possible to use withMapping like this as a shorthand :

val randomPerson = Fabrikate().random<Person> { config ->
    config.withMapping<String> { UUID.randomUUID().toString() }
}

Finally, you can create Fabrikate with a builder-like syntax :

val fabrikate = Fabrikate
    .withStandardMappings()
    .withMapping(myRandomPerson)

Pitfalls

Standard mappings

When a FabrikatorConfig is instantiated, none of the default mappings will be applied. If you want to make use of those, make sure to call .withStandardMappings().

Registration ordering

The register() method of FabrikatorConfig will override the already existing Fabrikator for that type. If you need to provide a custom Fabrikator for one of supported types and want to use the standard mappings also, make sure to call .register() for your custom Fabrikator after calling .withStandardMappings().

Supported Types

• Int
• Long
• Double
• Float
• Char
• String
• ByteArray
• BigInteger
• BigDecimal
• Instant
• LocalDate
• LocalTime
• LocalDateTime
• OffsetTime
• OffsetDateTime
• ZonedDateTime
• Date
• Year
• Month
• YearMonth
• Set
• List
• Map
• URI
• URL
• File
• UUID
• Duration

Acknowledgement

The original code is copied from Creating a random instance of any class in Kotlin by Marcin Moskala.