Fixture Factory

Sample factory is a code generator helping by writing tests. It allows to create data class instances filled with random data. Let's assume we have data class Car in the project.

data class Car(
    val brand: String,
    val model: String,
    val vin: VIN,
    val price: MonetaryAmount,
    val weight: Double,
    val productionDate: Instant
)

And we need an instance in the unit test case. First we create an interface for our factory. @Fixture annotation makes the magic.

@Fixture
interface Fixtures {
    fun sampleCar(): Car
}

Then, in the test class ...

 @Test
 fun `should drive a car` () {
    val factory = getFixtureFactory<Fixtures>()
    val car = factory.sampleCar()
    
    ...
 }

And a Car instance looks like this:

Car(brand=JCEVoI8CTe, model=y6XSn20rih, vin=VIN(vin=8KNU1xyhqc), price=PLN 0.42, weight=51.495863092903974, productionDate=2023-03-14T20:21:59.179562100Z)

If you need more control over some properties, factory methods should define params with default values.

@Fixture
interface Fixtures {
    fun sampleCar(weight:Double = 3.0, brand:String = "BMW"): Car
}

And all instances have fixed brand and weight properties

Car(brand=BMW, model=tTymibpcnC, vin=VIN(vin=E7XK8pbRwR), price=PLN 94.68, weight=3.0, productionDate=2023-03-14T20:33:56.981470400Z)